Law of Octaves

To know the Law of Octaves, we must first know what an Octave is?

Lets us now Define Octave: It could be defined as arrangement of eight note occupying the interval between two notes, wherein, one having twice or half the frequency of vibration of the other.

For example: In musical notes, after certain interval the note will repeat itself.

1	2	3	4	5	6	7
Sa	Re	Ga	Ma	Pa	Dha	Ni
Sa	Re	Ga	Ma	Pa	Dha	Ni

Now let us discuss Law of Octaves: It was proposed in the year 1865 by John Newlands (John Alexander Reina Newlands), British chemist, who classified the elements based on his law. According to the law, when elements placed in an increasing order of their atomic mass formula, every eighth element will show similarity in both physical and chemical properties. Since Newland proposed the Law of Octaves, in his honor the law is also called as Newlands Octaves.

We shall now study the Newlands Periodic Table; based on his law, Newlands arranged the known elements in a tabular form, wherein even row consists of seven elements and the eighth element was placed under the first element.

For example: The Newlands Periodic Table symbols is shown bellow, where in the lithium (Li) is the first element and the sodium (Na) is the eighth element, the Li and Na exhibit the similar physical and chemical properties, similarly, if we start arranging the elements in the increasing order of their atomic mass from Beryllium (Be) then the eight element would be Magnesium (Mg), both will exhibit similar chemical and physical properties.

Li	Be	B	C	N	O	F
Na	Mg	Al	Si	P	S	Cl
K	Ca

Newlands Periodic Table

Now we shall look into the drawbacks of the Newlands Octaves:

• The law does not hold good for the elements having atomic masses higher than calcium.
• Noble gases does not obey this law
• Classification was based on the atomic mass of an element is the periodic function of its chemical and physical properties concept.
• The law was valid till the Henry Moseley (1913), put forth the concept that the properties of an elements varies periodically according to the atomic number but not to the atomic mass. 

Carbon's position in the periodic table

Introduction :

Carbon is the element which is very important from the ancient times. It was found in the form of soot and charcoal and etc. It is also found in nature in various forms like petroleum, coal and CaCl₂ and magnesium carbonate. Carbon is also found in most of the foods which we used to daily in real life.

Carbon element is very reactive and found in both states i.e. in Free State and combined states. It is found in both forms such as amorphous and crystalline in Free State. Most common crystalline forms of carbon exist in nature are graphite and diamond. In the nature, the amorphous form of carbon does not exist. This amorphous form is made from organic material while some are manmade. This form is present as carbon dioxide present in air, coal, hydrocarbons like methane, natural gas etc, and proteins, carbohydrates and vitamins in the living organisms.

Carbon in Periodic Table:

The symbol of carbon element is C. It has atomic number of 6 having mass number 12. The three isotopes of carbon are:
¹²C₆, ¹³C₆ and ¹⁴C₆

1. The first element of IV A group is Carbon.

Properties of Carbon due to Ots Position in the Periodic Table:

The electronic configuration of IVA group shows that the members of this group have four electrons in the outer orbit.

Apart from carbon element, there are four other elements present in this group. They are silicon (Si), germanium (Ge), tin (Sn) and lead (Pb).

As we know, the carbon is  non-metal in nature. However if we go down in group IV A, the metallic character of this group’s elements increases.

Thus we can say that C and Si are non metals. Ge is metalloids and Sn, Pb are metals.

The elements of IV A group also have allotropy forms. For example carbon is found as graphite, diamond and coal etc.

The most important property of carbon is that it can form bonds with carbon itself which create the chain of carbon. This characteristic or property is termed as catenation. The carbon is the element which shows maximum catenation. Silicon shows this property to little extent and other elements of this group do not have catenation.

Likewise silicon exists as amorphous and crystalline forms.

The element carbon has tetra valency. With monovalent atoms, carbon can forms four single bonds.  For example: CCl₄

Formula for carbon tetrachloride

Introduction  :

Carbon tetrachloride is an organic compound , consists of two elements carbon as well as chlorine , which has the formula `C Cl_4`and having the IUPAC names as tetrachloromethane.
                                                                              
CHEMICAL FORMULA  :- `C Cl_4`
In the carbontetrachloride molecule four chlorine atoms are arranged in a tetrahedral way with carbon atom in the centre which makes it non polar in nature. A 3-d view of the carbontetrachloride molecule is shown as under:
                                          

Preparation of the Carbon Tetracloride :

Carbon tetrachloride can be prepared by the following three methods , we can prepare by any one of them.
1. By combining one molecule of methane with four molecules of chlorines , we get carbon tetrachloride as well as hydrogen chloride. Below is the reaction
         CH₄ + 4 Cl₂ → CCl₄ + 4 HCl
2 . By chlroination of carbon disulphide , we get carbon tetrachloride as well as sulphur monochloride .Below is the reaction
       CS₂ + 3Cl₂ → CCl₄ + S₂Cl₂
3. By the syntesis of the dichloromethane , we get two molecules of carbon tetra chloride    

C₂Cl₆ + Cl₂ → 2 CCl₄

Features and Uses of Carbon Tetrachloride :

• It has a boiling point of `76.7^o` C
• It is not able to dissolve iodine.and  non-polar in nature.
• It is a colourless liquid which is soluble with nearly mostly other liquids but is slightly soluble with water.
• Used in refrigerants, flour bleachings .
• It is a very good fire extinguisher as well as a dry cleaning liquid.
• Also used in pharmaceutical materials preparation.
• Used in lava lamps , used as a source of chlorine in organic chemistry.
• High use of carbon tetrachloride in open environment can effect the health also , lead to  kidney problems , liver problems , also led to the degradation of the nervous system.

Carbon Compounds

Introduction :

Carbon compounds play an important role in our daily life. Every living organism possess hydrocarbons. We cannot think of living life without carbon compounds. Carbon compounds with single bond between two carbon atoms are called alkanes and with triple bond are called alkynes e.g. ethane, ethene and ethyne. Apart from carbon and hydrogen, hydrocarbons also contain other elements, namely oxygen, nitrogen and sulphur etc.
The basic carbon compounds are - alkanes, alkenes and alkynes. Let us describe each of them:

Alkanes - Alkanes are also known as saturated hydrocarbons. In alkanes, the hydrogen and the carbon atoms are joined using the single bond. The simplest alkane is CH₄ or methane, which is as shown below. Examples of larger alkanes are waxes and saturated oils.

Alkanes are acyclic molecules. It is saturated. They are not very reactive.
Alkenes - An alkene is an unsaturated carbon compound. It contains atleast one carbon-carbon double bond. The general formula for alkenes is C_nH_2n. Example of the simplest alkene is Ethylene (C₂H₄).

Alkynes - These hydrocarbons have a triple bond between two carbon atoms. The general formula for alkynes is C_nH_2n-2. Alkynes seem to be more reactive, but are hydrophobic. They are also known as acetylenes.
Group of atoms in a structure that determines the characteristic reactions of a compound is called functional group. Few important functional groups are:
a) Alcohol
b) Aldehyde
c) Ketone
d) Carboxyl
e) Ester
Let us learn the naming of some of the carbon compounds:

Naming of Alcohols:

Alcohols are hydroxy derivatives of alkanes. When one hydrogen atom of alkane is replaced by a -OH group then formation of alcohol takes place. Alcohols are also called as alkanols. Alcohols have general formula C_nH_2n+1OH.
Alcohols are homologous series of compounds that contain - OH functional group. While naming alcohol letter 'e' from homologous series of alkane is replaced by 'ol' as shown:
Alkane                                                                                    Alcohol
Methane                                                                                 Methanol
Ethane                                                                                    Ethanol
Propane                                                                                  Propanol
When more than two carbon atoms are present in a carbon compound then while writing the name of a compound the position of carbon atoms is also specified.
E.g. CH₃ - CH₂ - CH₂OH      Propan -1 -ol

Naming of Carbonyl Compounds:

Aldehydes and ketones represent a family of organic compounds known as carbonyl compounds.

Naming of Aldehydes:
While naming aldehydes the letter 'e' of corresponding homologous series os alkane is replaced by 'al' as shown:

Alkane                                                                           Aldehyde
Methane                                                                        Methanal
Ethane                                                                           Ethanal
Propane                                                                         Propanal

Naming of Ketones:
While naming ketones, the letter 'e' of corresponding homologous series of alkane is replaced by 'one'.
E.g. The simplest ketone is acetone and IUPAC name is propan-2-one.
Few more members of ketone series are: Butan - 2 -one, Pentan - 3 - one etc.

Naming of Carboxylic Acid:

Carboxylic acids are homologous series of compounds having -COOH group. While naming carboxylic acids the letter 'e' of corresponding homologous series of alkanes is replaced by 'oic' as shown:
Alkane                                                                                            Carboxylic Acid
Methane                                                                                          Methanoic Acid (Formic Acid)
Ethane                                                                                             Ethanoic Acid
Propane                                                                                           Propanoic Acid

Electrochemical Reduction

Introduction

Electrochemical reduction is the process of chemical reduction that happens at the cathode of an electrochemical cell. Electrochemical reduction happens when an atom accepts an electron. Electrochemical reduction is one part of redox reactions, the counterpart being electrochemical oxidation.

Electrochemical Reduction

Redox means reduction-oxidation; these are known as the electrochemical processes that involve transfer of electron to or from a single molecule or an ion to another in a system. This reaction happens when an external voltage is applicable or by releasing chemical energy.
In electrochemical reduction, the electron rich molecule or ion donates one or more electrons and gets oxidised. The molecule that accepts these electrons gets reduced as now it has more number of electrons and reduced number of protons.
Reduction and oxidation as a rule happen in pairs. If one component of an electrochemical system gets oxidised, there will be another component in the same system that will get reduced. This is a redox reaction.
For reactions involving oxygen, the loss of oxygen means the reduction of the atom or molecule to which oxygen is added. In Organic compounds, like butane or ethanol, the gain of hydrogen implies reduction of the molecule from which it is lost.  Thus a reaction in which there is loss of oxygen or gain of hydrogen means there was electrochemical reduction.
The atom or molecule that loses electrons is known as the reductant, or reducing agent, and the atom or molecule that accepts the electrons is called the oxidant, or oxidizing agent. The oxidizing agent is always reduced in a reaction and the reducing agent is always oxidized.

Conclusion for Electrochemical Reduction

Electrochemical reduction is the process of gaining an electron by an ion or molecule in electrochemical processes. If there is electrochemical reduction in a process, there is bound to be and electrochemical oxidation in the same process simultaneously.

Exothermic endothermic chemical reactions

Introduction: there are two types of reactions on the basis of heat changes involved: exothermic reaction and endothermic reactions.

Exothermic reactions:
Those reactions in which heat is evolved are known as “exothermic reactions”.

For example:
(i) when carbon burns in oxygen to form carbon-di-oxide, a lot of heat is produced in this reaction:
                    C(s)       +    O₂ (g)   -------------------------->         CO₂ (g)          +        Heat
                Carbon          oxygen                                     carbon dioxide

The burning of carbon in oxygen is an exothermic reaction because heat is evolved in this reaction. AN exothermic reactions is indicated by the writing “+Heat” or “Heat energy” or just “+Energy” on the products’ side of an equation.

(ii)Respiration is also an example of exothermic reactions because energy is produced during this process. In respiration, glucose combines with oxygen in the cells of our body to form carbon dioxide and water along with production of energy:
C₆H₁₂O₆ (aq)     +         6O₂ (g)    ------------------------------->         6CO₂ (g)       +        6H₂O (l) +    Energy
(Glucose)                    (Oxygen)                                          (Carbon dioxide)           (Water)

Exothermic Endothermic Chemical Reactions : Endothermic Reaction

Endothermic reactions:
Those reactions in which heat is absorbed are known as “endothermic reactions”.

For example:
(i) When nitrogen and oxygen are heated to a very high temperature (of about 3000^o C) they combine to form nitrogen monoxide, and a lot of heat is absorbed in this reaction:
N₂ (g)         +       O₂ (g)      +    Heat   ---------------------->   2NO (g)
(Nitrogen)          (0xygen)                                             (Nitrogen monoxide)
The reaction between nitrogen and oxygen to form nitrogen monoxide is an endothermic reaction because heat is absorbed in this reaction. An endothermic reaction is usually indicated by writing “+Heat” or “+Heat energy” or just “+Energy” on the reactants side of an equation.
(ii)  All the decomposition reactions require energy ( in the form of light , heat or electricity) to take place. For example , when calcium carbonate is heated , it decompose to form calcium oxide and carbon dioxide:
      CaCo₃ (s)                +       heat  -------------------->        CaO (s)         +       CO₂ (g)
Calcium carbonate                                                     Calcium oxide          carbon dioxide

Ethane Chemical Formula

Introduction to ethane :

Ethane is an organic compound and it is the second member of alkane. The chemical or molecular formula of ethane is  C₂H₆. Ethane is an aliphatic saturated hydrocarbon. C₂H₆, the chemical formula of ethane was created synthetically by Michael Faraday in the year 1834. It was formed by the electrolysis of potassium acetate. The name ethane is derived from tther ( diethyl ether). The molar mass of ethane is 30.07g. Ethane is a colorless, odorless, and a flammable gas at standard temperature and pressure.  The melting point and boiling point of ethane are -181.76˚ and -89˚C respectively.   The 3D structure of ethane whose chemical formula is C₂H₆ .

Bonding of Ethane

There are two carbon atoms and six hydrogen atoms present in ethane. Both the carbon atoms are sp3 hybridized, so there will be overlapping of 8 sp3 orbitals, 2 from 2 carbon atoms and 6 from 6 hydrogen atoms, so the bond between two carbon atoms is the sigma bond.
The bond length between two carbon atoms is 154pm and between hydrogen and carbon is 110pm. The bond angle is 111.17˚.

Production of ethane:
Ethane is obtained by the separation method from methane by liquefying it at cryogenic temperatures.
The fractionating column is as shown below, ethane is obtained by heating crude oil in the furnace, then it is fed to the fractionating column. In fractionating column, the substances which have lowest boiling point can be extracted first. So, the gases of hydrocarbon from C1 to C4 which contains ethane escapes out at 20˚C. Similarly,  the number of hydrocarbons can be according to their boiling point.

Chemical Reactions of Ethane:

Chemical reactions of C₂H₆:

• Halogenation of ethane:

Ethane reacts with halogens like chlorine, halogen substituted ethane will form.
H₃C-CH₃  + Cl₂ ===> CH₃-CH₂-Cl + HCl.

• Reduction of ethane:

Ethane undergoes reduction in presence of Zinc dust which acts as catalyst gives ethene.
H₃C-CH₃ ===> H₂C=CH₂
Uses of Ethane:
Ethane has wide applications, few of them are as follows

• It is used to produce ethylene gas from steam cracking.
• It is used as a fuel and also used as refrigerant.
• It is used in bath soaks and was also used in gasing whales in world war II