Classification of Chemical Coordination

Introduction:

A metal or coordination complex is a structure which consist of a central atom or ion which is usually a metal being bonded to a molecules or anions array. Examples are ligands and complexing agents. Within a ligand, there is an atom that is directly bonded the atom in the centre or ion, this is called the donor atom. A chelate complex can be formed by polyadenylated ligand. At least one pair of electrons is donated by the ligand to the central atom/ion.

Compounds containing a coordination complex are called coordination compounds. The central atom or ion together with all ligands forms the coordination sphere.

Coordination points to the "coordinate covalent bonds" (dipolar bonds) between the ligands and the central atom.

Classification of Chemical Coordination

Metal complexes also known as coordination compounds; they consist of all metal compounds, aside from metal vapors, plasmas, and alloys. The study of "coordination chemistry" is the study of all alkali and alkaline earth metals, transition metals, lanthanides, actinides, and metalloids. Thus, coordination chemistry is the chemistry of majority of the periodic table. Metals and metal ions only exist in the condensed phases surrounded by ligands.

The different areas of coordination chemistry are classified according to the nature of the ligands. They are:

 1) Classical (or "Werner Complexes"): Ligands in classical coordination chemistry bind to metals via their "lone pairs" of electrons residing on the main group atoms of the ligand. Typical ligands are H2O, NH3, Cl−, CN−, en−

Examples: [Co(EDTA)]−, [Co(NH₃) ₆]Cl₃, [Fe(C₂O₄) ₃]K₃

2) Organo-metallic Chemistry: Ligands which are organic (alkenes, alkynes, alkyls) as well as "organic-like" ligands are found in organo-metallic chemistry like phosphines, hydride, and CO.

Example: (C₅H₅) Fe (CO) ₂CH₃

 3) Bioinorganic Chemistry: Ligands which are provided by nature, especially including the side chains of amino acids, and many cofactors such as porphyrins.

Example: hemoglobin.

Many natural ligands are Werner complexes especially including water.

4) Cluster Chemistry: Ligands which also include other metals as ligands.

Example Ru3(CO)12

Older classifications of isomerism

In the older literature, one encounters:

1) Ionisation isomerism states that the possible isomers arise from the exchange between the outer sphere and inner sphere. In this classification, the "outer sphere ligands," may combine with the "inner sphere ligands" to produce an isomer.

 2) Solvation isomerism occurs when an inner sphere ligand is replaced by a solvent molecule. This classification is absolute because it considers solvents as being distinct from other ligands.

What are chemical indicators

Introduction 
Substance which undergo some easily detectable change (such as change of colour, precipitation, etc.) during titration and which thereby indicate the equivalence point are called Chemical indicators.

Example:  Phenolphthalein, Methyl orange, Methyl red, Starch, etc.

Main Characteristics Of Chemical Indicators

Chemical indicators possess one color in the presence of an excess of the substance to be estimated, and another in the presence of an excess of the standard solution of the reagent used and thus these substances indicate the exact end-point.  A familiar example of an indicator is litmus, which is blue in the presence of an excess of alkali and red in the presence of excess of acid.
A good chemical indicator must possess the following two essential characteristics.

1. The color change of the indicator must be clear and sharp, i.e. it must be sensitive.  Thus, it would be useless if 2 or 3 c.c. of the reagent is sufficient to bring out the color change.
2. The Ph-range over which the color change takes place must be such as to indicate when the reaction is complete.

Classification Of Chemical Indicators

All well-known indicators can be classified in two ways; either on the environment in which they are used or on the basis of the types of titrations in which they are used.  In general, an indicator may be internal or external.

1. Internal indicator: If the indicator is added to the liquid which is being titrated, it is called an Internal indicator viz. litmus solution, Phenolphthalein, potassium chromate, etc.
2. External indicator: If the indicator is used outside the vessel in which the reaction is taking place, and drops of the liquid are taken out of the reaction vessel from time to time and mixed with the indicator, it is called external indicator.

Potassium ferricyanide, the most familiar example of external indicator, is used during the titration of ferrous ions as it gives blue color with ferrous ions and a brown coloration with ferric ions and thus tells us when a ferrous solution has been completely oxidized to the ferric state.  The indicator is used as external since if it is added to the ferrous solution to start with, it would have been reacted with it.

Explosive chemical reactions

Introduction :
Chemical reactions that releases energy are known as exothermic reactions.

Case I: When the reaction proceeds slowly, released energy will be dissipated smoothly and there will be few noticeable effects other than an increase in temperature.

Case II: On the other hand, when the reaction proceeds very rapidly, the energy will not be dissipated smoothly. A huge amount of energy can be deposited into a relatively small volume of atmosphere, then manifest itself by a rapid expansion of hot gases, which in turn can create a shock wave or propel fragments outwards at high speed.
There are three primary fields of application for these chemcial explosions: propellants, explosives and pyrotechnics.

Propellants works when they create a high gas pressure for moving projectiles or rockets and for similar uses.

Explosives works when they create a disruption of solid or liquid bodies, as in construction, mining or warfare.

Pyrotechnics works when they have effects that are mainly sound and light, but include many other varied applications, mainly on a small scale.

Fireworks are used as an application for entertainment, a show of light, noise and motion.

Some more examples:

Black Powder: Black powder was invented as a pyrotechnic substance, then it was applied as a propellant in firearms, and finally used in engineering and mining. The history of black powder and firearms relates to Cannon.

Smokeless Powder: Vielle discovered how to make a propellant from cellulose nitrate in 1886. The work was started with low-nitrogen guncotton, or pyrocotton, with 11%-12% of nitrogen, and plasticized it with ether and alcohol. Pyrocotton will dissolve completely in this solvent. This gel was rolled out into sheets and then the sheets were broken up into powder, after this the powder formed into grains, and these grains, mixed with various additives to control the rate of burning, chemical properties and stability in storage, made a propellant called smokeless powder that could replace gunpowder, and was more powerful.

Aromatic Explosives: One of the first aromatic explosives was picric acid, or trinitrophenol, C6H2(NO2)3OH. This particular explosive was first prepared in 1771 by Woulfe as a dye, and was also used in medicine, long before it was first employed as an explosive in 1830. Name was so given because of it's extremely sharp or bitter taste, and also in Greek word it means pikros, "sharp." It forms pale yellow crystals of density 1.76 g/cc, melting at 122°C and exploding above 300°C. It is too sensitive to heat to be poured into shells, and must be press-loaded, meanwhile another effect of it is corrosion of metals, forming sensitive picrates. The most famous aromatic explosive is trinitrotoluene, called TNT for short. TNT is deficient in oxygen, so makes a cloud of black smoke. It is a popular bursting charge for shells and bombs, replacing picric acid after World War I.

Atomic number 81

 Introduction :

• Atomic number 81 belong to P-block elements.
• Atomic number 81 is Thallium and chemical symbol is ‘Tl’ from periodic table.
• Thallium belongs to Group13 and period 6.
• General electronic configuration of p-block element is [Rare gas] nS² np^{1 to 6}
• Thallium has atomic number 81 and mass number 204.383 The data is obtained from the periodic table.
• Atomic number 81 was found in iron pyrites, crookesite, hutchinsonite, and lorandite.  It is obtained in the by-product of zinc and lead smelting.
• Electronic configuration of Thallium:
• 1S², 2S², 2P⁶, 3S², 3P⁶, 3d¹⁰, 4S², 4P⁶, 4d¹⁰, 4f¹⁴, 5s², 5p⁶, 5d¹⁰, 6S², 6P¹
• Electron per energy level: 2, 8, 18, 32, 18,3
• Number of Electrons (with no charge): 81
• Number of Neutrons (most common/stable nuclide): 123
• Number of Protons: 81
• Oxidation States: 3,1
• Crystal Structure of Atomic number 81 is Hexagonal.
• Density (293 K) of thallium is 11.85 g/cm³.
• In Greek thallos mean green twig, representation for bright green line in its spectrum.
• Thallium is a Soft gray metal that looks like lead.
• Sir William Crookes discovered Thallium in the year 1861 in England.
• Thallium belongs to metal group.

Thallium is very soft and malleable and at room temperature, it can be cut with a knife.  Thallium has a metallic luster, but by exposing to air, it quickly diminishes with a bluish-gray tinge that resembles lead. It is preserved by keeping it under oil.

Image of Thallium metal: Appearance of thallium metal is silvery white colour.
                                            


Properties of Atomic number 81

• Atomic radius and ionic radius of Group 13 elements: Atomic radius and ionic radius increases down the group from boron to thallium

Elements	Boron	Aluminum	Gallium	Indium	Thallium
Atomic radius (pm)	85	121	135	155	190
Ionic radius (pm)	41	53.5	76	94	102.5

• Ionization potential of Thallium:

      First Ionization potential: 6.1083 eV.
      Second Ionization potential: 20.428 eV.
      Third Ionization potential: 29.829 eV.

• Oxidation states of Atomic number 81: Group 13 elements exhibit oxidation state of +3.  Thallium exhibit oxidation state of +1 and +3.  It is exhibited when ns², np¹ electrons are involved in bonding.

                   Tl       : [Xe] 4f¹⁴, 5d¹⁰, 6s², 6p¹
                            Tl¹⁺     : [Xe] 4f¹⁴, 5d¹⁰, 6s², 6p⁰
                   Tl³⁺     :  [Xe] 4f¹⁴, 5d¹⁰, 6s⁰, 6p⁰

• Inert pair effect of Thallium: In Inert pair effect, the outermost s electrons to remain no ionized or unshared in compounds of post-transition metals (or p-block elements). The term inert pair effect is frequently used in relation to the increasing stability of oxidation states that are 2 less than the group valence for the elements of groups 13, 14, 15 and 16. The term "inert pair" was first proposed by Nevil Sidgwick proposed the term "inert pair" in 1927. As an example in group 13 the Tl has+1 oxidation state and it is the most stable one and Tl^III compounds are comparatively less. The stability of Group 13 elements is given in the order,

                                        Al^I < Ga^I < In^I < Tl^I.

• Melting point (M.P.) and boiling points (B.P.) of Group 13 elements: Melting point depends on the size of the atom.  Smaller the atomic size, higher is the meting point. Boiling point decreases from boron to thallium. 

Elements	Boron	Aluminum	Gallium	Indium	Thallium
M.P.  (0C)	4275	2740	2475	2350	1745
B.P.  (0C)	2300	933.25	302.9	429.75	577

• Isotopes of Thallium:  There are 25 isotopes in thallium.  Atomic masses ranges from 184 to 210. Stable isotopes are only ²⁰³Tl and ²⁰⁵Tl .  ²⁰⁴Tl is the most stable radioisotope which is having a half-life of 3.78 years.

Uses of Thallium

• Thallium sulphate is odorless and tasteless and was once widely used as rat poison and ant killer. Since 1972 it is prohibited.
• To treat ringworm, other skin infections and to reduce the night sweating of tuberculosis patients, thallium salts were used. However it is limited due to their narrow therapeutic index.

Chemical reaction of Thallium

• Chemical reaction of thallium with air: When thallium metal is heated to red hot in the presence of air, thallium (1) oxide which is poisonous is formed.

                 2Tl _(s) + O_{2 (g)} → Tl₂O _(s)

• Chemical reaction of thallium with water: When Thallium metal is exposed to moist air, it tarnishes slowly and then it dissolves in water to form thallium (1) hydroxide which is poisonous is formed.

                2Tl _(s) + 2H₂O _(l) → 2Tl (OH) _(aq) + H_{2 (g)} ↑

• Chemical reaction of thallium with halogens: Thallium metal reacts rapidly with halogen to form dihalides.  Thallium (111) fluoride, thallium (111) chloride and thallium (111) bromide are formed.  All these are poisonous.

                                        2Tl(s) + 3F₂ (g) → 2TlF₃(s)
                                        2Tl(s) + 3Cl₂ (g) → 2TlCl₃(s)
                                        2Tl(s) + 3Br₂ (l) → 2TlBr₃(s)

• Reaction of thallium with acids: Thallium reacts with sulphuric acid and hydrochloric acid slowly

Calculating percent yield

The predicted yield is determined by the masses used in a reaction and the mole ratios in the balanced equation. This predicted yield is the "ideal". It is not always possible to get this amount of product. Reactions are not always simple. There often are competing reactions. 

 For example, if you burn carbon in air you can get carbon dioxide and carbon monoxide formed. The two reactions occur simultaneously. Some carbon atoms end up in CO and others end up in CO2. The typical calculation in a starting class assumes that there is only one path for the reactants. This is an over simplification.You know for example from real life that food is not always converted to energy. If you eat a cookie, some of it could end up stored as "fat" Ugh!

Chemists, like all other people, aren't perfect. When a chemist does a synthesis, she will end up creating less product than expected because of spills, incomplete reactions, incomplete separations, or a dozen other reasons. The percent yield is a way of measuring how successful a reaction has been.

To compute the percent yield, figure out how much product you should have made by using basic stoichiometry. (Note: this may involve a limiting reagent problem.) Then simply divide the amount of stuff you did form by the expected amount and multiply by 100%. If you get a number > 100%, you've made a serious error someplace.

Obviously, you want a high percent yield: if you have a ten step synthesis where the product from one reaction ends up as the reactants for the next and each synthesis has 90% yield, you'll end up with only ~35% yield for the overall reaction.

Example: You burn 10.0 grams of methane in an excess of oxygen and form 19.8 grams of water. What was your percent yield?

Solution : First, you need to find out how much product you would expect to make using basic stoichiometry. The reaction of methane with oxygen is shown below

CH4(g) + 2O2(g) -> CO2(g) + 2H2O(g)

You start with 10.0 grams of methane, which has a molecular weight of 16.04 g/mole, so you have 10.0 g/16.04 g/mole = 0.623 moles of methane.

The ratio between methane and water is 2 water for every 1 methane, so you expect to form

0.623 moles CH4 * 2 moles H2O/1 mole CH4 1.25 moles H2O

Now convert back to grams: the mole weight of water is 18.02 g/mole, so you should form

1.25 moles H2O * 18.02 g/mole = 22.5 g water

If the reaction had gone perfectly. You only formed 19.8 however, so your percent yield is

% yield = mass created/mass expected * 100%

% yield = 19.8 g/22.5 g = 88.0%

Standard gas volume

Introduction :
Each gas is characterized by the property of volume.  Volume is a space occupied by a gas. Volume is dependent on the temperature.  More the temperature more would be the volume.  Standard gas volume is defined as volume occupied by a gas at standard temperature and pressure.

 What are the figures for standard pressure and temperature?  The figures of standard pressure and temperature are adopted at 1 atmosphere and 273 degree Kelvin.  For the gas loss, the value of the units of pressure and temperature are always taken as atmosphere and degree kelvin.  The volume occupied by a gas at these standard conditions is called as standard volume.

Equations to find standard gas volume

Boyle established the relationship between pressure and the volume.Charles established the relation between pressure and temperature.
From both of these equations the universal gas law equation was derived and from the same ideal gas law equation was derived.
The ideal gas law equation is PV =nRT, here 'P' is pressure, 'V' is volume, 'n' is number of moles, 'R' is the gas constant and 'T' is temperature.  If the values for standard pressure and temperature are substituted at 1 atmosphere and 273 degree kelvin, the volume occupied by 1 mole of a gas comes to 22.4 liters.
Thus 22.4 liters is a standard volume of 1 mole of any gas.  This equation was derived by Avogadro. He quantified the volume occupied by 1 mole of gas at standard conditions

Illustration to show standard gas volume

The standard volume has been useful to find many other things in practical chemistry.Let us consider following problems.

Problem 1:
                   Find volume occupied by 64 grams of oxygen at STP
                                                       Or
                       Find the standard volume of 64 gms of oxygen.

Answer:  64 no. of moles of oxygen is = 64 / 32 = 2.
               If 1 mole occupies 22.4 litres, 2 moles would occupy 44.8 liters.

Problem 2:
                   Find the moles of the gas if the standard volume is 100 liters.

Answer: 1 mole occupies 22.4 liters,
             so 100 liters is occupied by 100 / 22.4 = 4.464 moles.

Percent volume concentration

Introduction :
Concentration of a solution depends upon the amount of solute present in the solution.  The concentration of the solution is expressed in many ways.  One of the important way of expressing the concentration is percent volume concentration.  Other means of expressing the concentration are mass percent which is nothing but the mass of the solute present in the solution expressed as percentage that is (mass of the solute/mass of solution) x 100.  Another way of expressing the concentration is by molarity it is the mole of solute present in a liter of the solvent it is expressed as mol/litre.  Yet another way of expressing the concentration is by molefraction is the fraction of moles that is present in the whole of the solution.  That is if two component A and B are present in the solution.  the mole fraction of A is the number of moles of A/moles of A + moles of B.

Concentration as volume percent:

In most of the liquid samples the concentration is expressed by volume percent
volume present = (volume of the solute/volume of the solution) x 100.  This is the easiest method of expressing the concentration of a liquid solution.
For example if you have 10%volume/volume of antifreeze that is ethylene glylcol in water it means that there is 10mL of ethylene glycol in 100mL of the soluiton or 10L of ethylene glycol in 100L of the solution

Problems on percent volume concentration:

Find out the volume percentage of ethanol when 10mL of ethanol is mixed in 190mL of the water?
Soluiton:

Volume of the solute that is ethanol is 10mL

volume of the solvent that is water is 190mL

total volume of the solution = volume of the solute + volume of the solvent = 10mL + 190Ml= 200mL
So volume percentage =(volume of solute  / volume of solution) x 100
= (10 / 200) x 100 = 5% v/V

Iupac nomenclature for organic compounds

IUPAC Rules for Nomenclature:

(i).Root words:

C1 -Meth, C2 -Eth, C3-Prop ,C4-Buta, C5- Penta, C6- Hexa, C7- Hepta,C8- Octa,C9-Nona,C10-Deca

(ii).Primary suffix:

                               Alkane   - C-C-       -ane
                               Alkene     -C=C-       -ene
                             alkyne       -C=_C-      -yne
1.Longest sum rule:
the longest continuous chain of carbon atoms is considered for naming the carbon compound, the prefix in the name of the compound depends on the number of carbons present in the compound.

2.Least Sum Rule:
In numbering the carbon atoms in the parent chain start at the end which  results in the use of lowest number for the substituent carbon atoms.

3.When identical substituent are present on the same carbon atom,the position of the substituent is repeated

4.if the carbon chain contain 2 or more than 2 identical substituent,then di- tri- tetra- words are used to indicate the number of substituents.

5.If the number of different groups are attached to the parent the chain ,then the naming is done in two ways:
(i). according to the IUPAC rules
(ii) the name is given to the compound following the increase in order of complexity of the group

6.when a carbon compound  has carbon chain having the same no.of carbon atoms,they having more number of branches is selected as the parent chain

7 If a carbon chain contains substituents which are at equal distance either from left are right side counting is done in such a way that the least number is given to substituens

8 When the main carbon chain in a carbon compound carries a branch which again contains a substituent,the position of the substituent in the branch is written in the brackets.

IUPAC Rules for naming Poly functional compounds:

A molecule can contain more than one functional group called as polyfunctional group,the functional group which specifies its class is called the principle functionl group the other functional groups are refered to as ' substituents'

Nomenclature Priority for determining the principle functional group.Highest priority at the top.
suffixes for functional groups:
Caboxylic acid     -COOH   (  -oic acid )
sulphonic acid    -SO3H  (sulphonic acid)
Ester                     - COOR ( -alkyl -  oate)
Acid halide           -COX  ( -oyl chloride)
amide                  -CO NH2 ( -amide)
nitrile                  -CN (-nitrile)
aldehyde         -CHO  (-al)
ketone             -CO-   (-one)
alcohol          -OH ( -ol)
amine             - NH2  (-amine)
ethers            -O-  (ether)
alkene          -C=C- (ene)
alkyne         -C=_C-   (-yne)


1.Identify principal functional group.this gives class name of  the structure.

2. Number the longest chain containing the principal functional group from the end closer to it.

3.Write the parent name corresponding to the no.of cabons in the longest chain.

4 Arrange the substituents names with position numbers in alphabetical order.

5.Prefix substituent name with the parent name.

6.The following functional groups are always named as substituents ,their names prefixed with the parent name.
ex:Cl - chloro; Br - bromo ;I -iodo ;F-flouro ;CN - cyano ; R - alkyl, OR - alkoxy ; NH2 -amine;NO2 -nitro  etc..

IUPAC Nomenclature rules with example:

7.Identify double/triple bonds. Number them with the number of the carbon atom at the head of the bond (i.e the carbon atom with the lesser number that it is attached to). For example a double bond between carbon atoms 3 and 4 is numbered as 3-ene. Multiple bonds of one type (double/triple) are named with a prefix (di-, tri-, etc.). If both types of bonds exist, then use "ene" before "yne" e.g. "6 13 diene 19 yne". If all bonds are single, use "ane" without any numbers or prefixes.

8. Arrange everything like in  this way: Group of side chains and secondary functional groups with numbers made in step 3 + prefix of parent hydrocarbon chain (eth, meth) + double/triple bonds with numbers (or "ane") + primary functional group suffix with numbers.
      Wherever it says "with numbers", it is understood that between the word and the numbers, you use the prefix(di-, tri-)

   9. Add punctuation:
         1. Put commas between numbers (2 5 5 becomes 2,5,5)
         2. Put a hyphen between a number and a letter (2 5 5 trimethylhexane becomes 2,5,5-trimethylhexane)
         3. Successive words are merged into one wordform (trimethyl hexane becomes trimethylhexane)
            NOTE: IUPAC uses one-word names throughout. This is why all parts are connected.

Ex:  CH3-CH(OH)-CH2-CH(CH3)-COOH

         5       4             3         2               1

From priority order -COOH  have higher rank ,therefore -COOH is the principal functional group.the structure is named as a carboxylic acid.
Longest chain : 5 carbons
so,parent name = pentanoic acid
Order of substituent 4-hydroxy -2-methyl
therefore,Name of the compound : 4-Hydroxy-2-methyl pentanoic acid.

Sound wave absorption

 Introduction :                                            
Sound waves travel in air as progressive longitudinal waves. Elasticity and inertia of the air  enable the sound wave to propagate with certain velocity. Sound cannot be transmitted through vacuum. It can travel through any solid, liquid and gas. All the frequencies of the vibrating bodies can not produce the sensation of hearing.

Sound  is a type of energy propagated in longitudinal waves. The source of sound could be any body which is vibrating. Some of the  examples are  a tuning fork which is excited, the wire of a stringed instrument being plucked , a bell which is struck with a hard thing,  etc.  When a sound wave is incident on any surface, a part of  the incident energy is always absorbed. Absorbption of  sound energy  vary  with different substances.

Thick screens or curtains, mats, carpets, wood, card boards are some of the examples of sound absorbers. Human bodies are very good absorbers of sound.  Best absorbers are those which absorb sound completely. Open windows and doors are therefore perfect absorbers. The characteristic absorption of a surface can be different at different frequencies.

Absorption coefficient of sound wave:

Absorption coefficient :  The absorption coefficient of a surface is defined as the ratio of the sound energy absorbed by the surface to the sound energy absorbed by an open window of equal area in the same time.

If Es  and Ew  are the amounts of sound energies absorbed by a given surface and an open window of the same area during same time, then

              The absorption coefficient        a     =    `(Es)/(Ew)`

Thus if  'a'  is the absorption coefficient of a surface and s is the surface area, the sound energy absorbed by it is given by  A  =  as.  Absorption coefficient 'a' has no unit but the SI unit of 'as' is metric sabin.

The absorption coefficients of certainsubstnces at a frequency of 512 Hz are given below.

S.No          Substance             Absorption Coefficient

1.               Marble                         0.01

2.               Glass                            0.028

3.               Carpet                          0.2

4.               Heavy Curtains             0.52

5.                Fibre glass                   0.69

6.              Open window                1.00

Doppler effect sound

Change in frequency of a wave for an observer which is moving with respect  to the source is called Doppler Effect. It was first proposed by Austrian physicist Christian Doppler in 1842. In day to day life we observe this phenomenon when a vehicle sounding a siren moves towards or away from an observer. The received frequency is higher (compared to the original emitted frequency) when source is coming nearer, it is identical at the instant of passing by, and it is lower when souce is moving away.

In mathematical form we write Doppler Effect as follows:
f= (V + Vr) / (V + Vs) * fo
Where:
V is the velocity of sound waves in the medium

Vr is the velocity of the receiver relative to the medium; taken positive if the receiver is moving towards the source.

Vs is the velocity of the emitting sound source relative to the medium; taken positive if the source is moving away from the receiver.

The frequency is decreased if either receiver or sound source moving away from the other.
Analysis

In Doppler Effect actually the frequency of the sounds that the source emits does not change. Let’s take a daily life example to understand what really happens. Suppose you throw one ball every second in your friend's direction. Assume that balls travel with constant velocity. If you are stationary, your friend will receive one ball every second. However, if you are moving towards your friend, he will receive balls more frequently because the balls will be less spaced out. The inverse is true if you are moving away from your friend. So it is actually the wavelength which is affected; as a consequence, the received frequency is also affected. It may also be said that the velocity of the wave remains constant whereas wavelength changes; hence frequency also changes.

Reflection of sound waves

A bell ringing rapidly, a drum moving up and down to the beat and a reverse rating harp string are all examples of objects that make sounds.
In this article let us learn about the reflection of sound waves.

Learning reflection of sound waves

Have you ever shouted into a well or inside an empty hall or in a cave? One can hear their own voice after a short time. Why is it happenning ? It happens because the sound of your voice is reflected from the walls.
We can also try this by shouting  into a well or by the side of a steep hill. This phenomenon of hearing your own sound again is called an echo. The rolling of thunder is largely due to successive reflections from clouds and land surfaces. For the reflection of sound waves, we need an extended surface, or obstacle of large size which need not necessarily smooth or polished.

Learning reflection of sound waves from one medium to other:

Generally, when sound waves in one medium strike a large object of another medium such as air, a wall, etc… , a part of the sound is reflected, and the remainder is sent into the new medium. The speed of the sound in the two mediums and the densities of the medium help to determine the amount of reflection. If the sound travels at about the same speed in both the materials and both have about the same density, little sound will be reflected, instead most of the sound will be transmitted into the new medium. If the speed differs greatly in the two and their densities are greatly different, most of the sound will be reflected.
When you shout at a brick wall most of the sound is reflected, because brick is denser than air.

I like to share this Sound Wave Energy with you all through my blog.

Check my best blog Sinusoidal wave equation.

Sinusoidal wave equation

We found that the disturbance (whether pulse or wave, transverse or longitudinal) depends on both position x and time t. If we call the displacement y, we can write y = f(x,t) or y(x,t) to represent this functional dependence on time and position. In the example of the transverse pulse traveling along a Slinky as pictured in Fig. 17-2,

y(x,t) represents the transverse (vertical) displacement of the Slinky rings from their equilibrium position at given position x and time t. (Alternatively, in the longitudinal wave on the Slinky shown in Fig. 17-1, y(x,t) could represent the number of Slinky coils per centimeter at a given x and t.)
We can completely describe any wave or pulse that does not change shape over time and travels at a constant velocity using the relation y = f(x,t), in which y is the displacement as a function/of the time t and the position x. In general, a wave can have any shape so long as it is not too sharp. The trick then is to find the correct expression for the function, f(x,t).

Fortunately, it turns out that any shape pulse or wave can be constructed by adding up different sinusoidal oscillations. This makes the description of sinusoidal waves especially useful. So, for the rest of this section we'll discuss the properties and descriptions of continuous waves produced by displacing a stretched string using a sinusoidal motion like that shown in Fig. 17-3b. We will start by using the equation we developed in Chapter 16 to describe for sinusoidal motion at the location of a single piece of string. As we did in looking through the slit in Fig. 17-5, we will only let time vary. Next we can consider how to describe a snapshot that records the displacement of many pieces of the string at a single time. Finally, we can combine our snapshot with the results of peeking through a slit to get a single equation that ought to describe the propagation of a single sinusoidal wave. Basically we are trying to describe the displacement y of every piece of the string from its equilibrium point at every time. We are looking for y(x,t).

Looking Through a Slit: Sinusoidal Wave Displacement at x = 0
If we choose a coordinate system so that x = 0 m at the left end of the string in Fig. 17-3b, then the motion at the left end of the string can be described using Eq. 16-5 with the string displacement from equilibrium represented by y(x,t) = y(0,r) rather than by simply y(t). To simplify our consideration we assume that the initial phase of the string oscillation at x = 0 m and t = 0 s is zero. This gives us

where the angular frequency can be related to the period of oscillation by to = 2irlT. Although we use the cosine function in Chapter 16 to describe simple harmonic motion, it is customary to use the sine function to describe wave motion. As we mentioned in Chapter 16, when a sine function is shifted to the left by v/2 it looks like a cosine function. So we can also describe the same string displacement as a function of time at x = 0 m as

Note that using the sine function requires a different, nonzero initial phase angle given by ir!2. If we locate our slit at another nonzero value of x as shown in Fig. 17-5, then the initial phase (at t = 0 s) will often turn out to be different from w/2. In fact this initial phase is a function of the location x of the piece of string we are considering.
A Snapshot: Sinusoidal Wave Displacement at t = 0

Imagine that the man has been moving the end of the string up and down as shown in Fig. 17-36 for a long time using a sinusoidal motion. Instead of looking through a slit as time varies, we take a snapshot of the string at a time t = Os similar to that shown in Fig. 17-36. Then we expect our snapshot to be described by the equation

where A: is a constant and the "initial" phase when x is zero must also be tt!2. Note that if the snapshot of the string were taken at another time, the initial phase would probably be different.

Combining Expressions for x and t
Equation 17-1 describes the displacement at all times for just the piece of string located at x = 0 m. Equation 17-2 describes the displacement of all the pieces of string at t = Os. We can make an intelligent guess that the equation describing y(x,t) is some combination of these two expressions given by
y(x,t) = Ysin[(foc ± cot) + tt/2)], (17-3)

where tt/2 represents the initial phase when x = 0 m and t - 0 s for the special case we considered. 

In general we can describe the motion of our sinusoidal wave with an arbitrary initial phase by modifying Eq. 17-3 to get
 y(x,t) = Ysin[(fct ± tot) + 4>q)] (sinusoidal wave motion, arbitrary initial phase), (17-4)
where <f>₀ is the initial phase (or phase constant) when both x = Om and t = Os. The ± sign refers to the direction of motion of the wave as we shall see in Section 17-5. In cases where the initial phase is not important, we can simplify Eq. 17-3 by choosing an initial time and origin of the x axis that lies along the line of motion of the wave so that <t>o = 0 rad.

Atomic number 28

Introduction :
d – block elements are also called transition elements. Transition metals are those elements which contain partially filled d- sub shells either in their atoms or in their common oxidation states. Nickel is a silvery white metal and takes a high polish. Nickel is hard malleable, ductile, ferromagnetic and fair conductor of heat and electricity. Atomic number 28 belongs to Iron – cobalt group. 'Ni' is commercially obtained from pentlandite and pyrrholite of the subdury region of Ontario.
Characteristics of Atomic number 28:

• The element in the periodic table which has atomic number 28 is Nickel. 
• 'Ni' has mass number 58.6934. 
• 'Ni' has oxidation state of 2 and 3. 
• Atomic number 28 has electronic configuration [Ar]4s²,3d⁸. 
• Nickel has chemical formula ‘Ni’.
• Atomic number 28 belong to Period 4 and Group 10.
• 'Ni' belongs to d - block elements. 

Properties of atomic number 28:

• Oxidation states of 'Ni': The elements exhibit variable oxidation states depending on the number of electrons participating in the bonding. Ni has oxidation states 2 and 3. 
• Colors of transition metal ions:  When the visible light of wavelength 400 to 700 nm is passed through a solution of a transition metal compound, it absorbs a particular frequency of radiation and transmits the remaining colors.
• Magnetic properties of 'Ni':  The paramagnetic behavior is highly pronounced in case of iron, cobalt and nickel. Hence they are called ferromagnetic substances.
• Formation of complexes by 'Ni': These metal ions have a great tendency to combine with a large number of molecules or ions called ligands and form complexes. The bond between a metal ion and a ligand is coordinate. Hence, complex compounds are also known as coordination compounds.
• Chemical reaction: Nickel carbonyl can be oxidized, Chlorine oxidizes nickel carbonyl into NiCl₂, releasing carbon monoxide gas.

               2Ni(CO)₄  +  2ClCH₂CH=CH₂    ====>  Ni₂(μ-Cl)₂ (η³-C₃H₅)₂  +  8CO

• Catalytic properties of transition metals: Many transition metals and their compounds are used as catalysts in several inorganic and organic chemical reactions. Nickel catalyst is used in the hydrogenation of oils.                                                                                       Oils +  H₂    →  Fats
• Isotopes of Nickel: ⁵⁸Ni, ⁶⁰Ni, ⁶¹Ni, ⁶²Ni and ⁶⁴Ni are five stable isotopes of Nickel. ⁵⁸Ni being the most abundant.  ⁶²Ni is one of the most stable nuclides.
• Reaction of 'Ni' with halogens:

             Ni_(s)    +    cl_2(g)   ====>    NiCl_2(s)     (Yellow)
             Ni_(s)    +    Br_(g)    ====>    NiBr_2(s)     (Yellow)
             Ni_(s)    +    I_2(g)     ====>    NiI_2(s)       (black)

• Reaction of Nickel with acids:

             Ni_(s)     +   H₂SO_4(aq)  ====>  Ni²⁺_(aq)  +  SO^2-_(aq)  +  H_2(g)  

• Reaction of Nickel with air:

    Nickel metal does not react with air under normal condition. Finely divided Nickel metal readily reacts with air. At higher temperatures, the reaction appears not to proceed to completion but give some nickel(ll) oxide.
            2Ni_{(s)    +}    O_2(g)    ====>  2NiO_(s)                                                                                        

Uses of Atomic number 28:

• It is used in many industrial and consumer products, including stainless steel, magnets, coins, rechargeable batteries, electric guitar strings and special alloys. 
• 'Ni' is used in plating and as a green tint in glass. 
• Atomic number 28 is a metal alloy and its chief use in the nickel steels and nickel cast iron. 
• 'Ni' is widely used in many alloys, such as nickel brasses and nickel bronze. etc.
• Raney Nickel, a finely divided form of metal is alloyed with aluminum which absorbs hydrogen gas. 

Isotopes of carbon

Introduction to Carbon:
The element with atomic number 6 in the periodic table refers to Carbon which belongs to group 14.  This element is widely distributed in most of the planets.  Carbon is a nonmetallic and tetravalent element and it forms covalent bonds.  The common oxidation states of carbon are +4 in organic compounds and +2 in carbon monoxide and transition metal complexes.  Diamond is the hardest material of carbon where as ceraphite is the softest material.   Mainly there are three allotropes of carbon fullerenes, diamond and graphite and some other forms are ionsdaleite, buckminsterfullerene and also carbon nanotube.
Allotropic forms of element with atomic number 6:
Fullerene                                 
     

Isotopes of carbon:

Among seven isotopes carbon has two stable isotopes. Those two isotopes of carbon are carbon-14 which is a naturally occurring radioisotope, it is used in carbon dating. Carbon- 13 which forms only 1.07%. Carbon-8 is the shortest lived isotope. Carbon-19 is the isotope which exhibits nuclear halo.
Compounds of carbon:
In atmosphere, carbon is found in combination with other elements like oxygen, hydrogen etc.  For ex: carbon dioxide, carbon monoxide, carbon disulfide, carbon tetra fluoride, chloroform, carbon tetrachloride, methane, ethylene, acetylene , benzene , acetic acid its derivatives.
Organic compound containing carbon (carbon tetra fluoride):

Properties of carbon:

• Atomic mass: 12
• Appearance: solid
• Electronic configuration: 1s² 2s² 2p² or [He] 2s² 2p²
• Density: 1.8-3.5g/cm³
• Melting point: 3915K
• Oxidation states: +4, +2
• Vander walls radius: 170pm

Applications of carbon:
1. Without carbon life could not exist because it plays an important role.
2. Carbon-14 which is naturally occurring isotope is used in carbon dating.
3. Allotrope of carbon (graphite) is used in pencil leads.
4. Hydrocarbons in combination with carbon are used in the production of gasoline and kerosene.
5. In nuclear reactors, it is used as neutron moderator.
6. It is (charcoal) used in artwork as a drawing material.
7. Cellulose is a natural carbon containing polymer used in maintaining the structure of plants.
8. Synthetic carbon is used in the production of plastics
9. It is used in diamond industries.

10. Now a day’s used in the production of carbon nanotube.

Atomic structure of Iron

Introduction 
There is a need at all levels of the study of science to present the correct picture of any substance. Here is an attempt to present the correct picture of the Iron atom, which is best described in terms of its orbital structure and orientation.
Occurrence: Iron is one of the more common elements on Earth. It makes up about 5% of the Earth's crust. Most of this iron is found in various Iron oxides, such as the minerals; Hematite, Magnetite, and Taconite. The earth’s core consists largely of a metallic iron-nickel alloy. Although rare, these are the major form of natural metallic iron on the earth's surface.

Atomic structure of Iron

The atomic number of Iron element is 26, which indicates the presence of 26 protons and 26 electrons in its atom.
Naturally occurring Iron consists of four isotopes:
a) 5.845% of radioactive ⁵⁴Fe (half-life: >3.1×10²² years) Number of neutrons, n = 28.
b) 91.754% of stable ⁵⁶Fe, n = 30.
c) 2.119% of stable ⁵⁷Fe, n = 31.
d) 0.282% of stable ⁵⁸Fe, n = 32.
E) ^{6 0}Fe is an extinct radionuclide. n = 34.
Nucleus:
The nucleus of Iron (Fe) atom is made of 26 protons and 30 neutrons (is most abundant).  The total number of electrons in Iron atom is 26, which is equal to that of protons, which maintains the neutrality of the atom.   But, Iron has got two stable oxidation states, +2 and +3.
Electron distribution:
The ground state electronic configuration of Iron atom is given by:
  (1s²)    (2s²2s⁶)    (3s²3p⁶3d⁶)    (4s²)

As it is seen in the electronic configuration, there are four shells available in the Iron atom.
The first energy level - K shell (n=1) - consists of 2 electrons in s-orbital, spherical in shape.
The second energy level - L shell (n=2) - consists of 8 electrons, out of which 2 in s-orbital and 6 in p-orbital (dumb bell in shape).
The third energy level - M shell (n=3) - consists of 14 electrons, out of which 2 in s-orbital and 6 in p-orbital (dumb bell in shape) and 6 in d-orbital (double dumb bell in shape).
The fourth energy level - N shell (n=1) - consists of 2 electrons in s-orbital.
Whenever Iron is oxidized, the electrons are removed from the outermost shell.  An octet electronic configuration is attained when +3 state is reached, which is half filled d-orbital state. So, Fe⁺³ is most stable state of Iron.
 (1s²)    (2s²2s⁶)    (3s²3p⁶3d⁵)    (4s⁰)
Iron is more stable, when it is oxidized.  So, it has a very high tendency to liberate electrons and get converted into Ferric ion, which is reasonable by its atomic structure. This is the reason why Iron gets rust.

Significance of atomic structure

The knowledge of the atomic structure is very useful in describing the chemical as well as physical properties associated with the element. Precisely, it can be said that the secrete of life is hidden in the atomic structure.

Atomic number 27

Introduction :
The word ‘atomic number 27’ refers to Cobalt which is having the atomic number 27. The number of protons in a nucleus determines the identity of the atom is called as ‘atomic number’.  It is represented by the letter Z. For example a hydrogen atom contains one proton, so the atomic number of hydrogen is one (Z=1) similarly the atomic number of cobalt is 27 (Z=27).
Swedish chemist Georg Brandt (1694–1768) is credited with discovering cobalt (atomic number 27) circa 1735. The word cobalt (atomic number 27) is derived from the German kobalt, from kobold meaning "goblin", a term used for theory of cobalt (atomic number 27) by miners.
Occurrence:
Cobalt (atomic number 27) occurs in copper and nickel minerals and in combination with sulfur and arsenic in the sulfidic cobaltite minerals.

Method of Extraction:

1. Froth flotation process:
It is a process for selectively separating hydrophobic materials from hydrophilic. This is used in several processing industries.
Froth flotation process is based on the principle that the metallic sulphide particles of the ore are preferentially wetted by oil and gangue particles by water.

                                                                                                 Froth flotation process
In this process, the finely divided ore is added to a large amount of water contained in the tank. Certain oils like pine oil, eucalyptus oil etc, are added.  A current of compressed air is circulated through the water in the flotation tank. The metallic ore particles are preferentially wetted by the oil froth and rise to the surface along with the froth. The gangue material is wetted. Hence it settles at the bottom.
2. Roasting process:
It is a process in which the ores are heated to a high temperature below their melting point in the presence of excess of air. During this process, the moisture escape and the impurities like sulphur, arsenic, etc are oxidized to their volatile oxides. The messes become porous. It is generally carried out in a reverberatory furnace.
                        S +O₂ → SO₂↑
                         As  +  O₂  →  As₂O₃↑
       Sometimes, the sulphide ore are oxidized to sulphates
                   2ZnS + 3O₂ → 2ZnO + 2SO₂

     Roasting process

Applications of Cobalt (atomic number 27)::

• It is used in batteries.
• It is used as catalysts.     
• It is used as a pigment and coloring.
• It is used in a biological role.
• It is used for electroplating.
• It is used for electroplating due to its appearance, hardness, and resistance to oxidation.