metal non metal class 10 one liner/ mcq question

 

CARBON AND ITS COMPOUND

 

Carbon is the 4th most abundant substance in universe and 15th most abundant substance in the earth’s crust.

The atomic number of carbon is 6. Its electronic configuration is 1s² 2s² 2p⁶.its valancy is 4.  It requires 4 electrons to achieve the inert gas electronic configuration. But carbon cannot form an ionic bond.

It could gain four electrons forming C^4- cation. But it would be difficult for the nucleus with six protons to hold on to ten electrons.

It could lose four electrons forming C⁴⁺ Anion. But it requires a large amount of energy to remove four electrons.

Thus, carbon overcomes this problem by sharing of its valence electrons with other carbon atoms or with atoms of other elements.

Covalent Bond:

The bond formed by mutual sharing of electron pairs between two atoms in a molecule is known as Covalent Bond.

Types of Covalent Bond:

·         Single Covalent Bond: When a single pair of electrons are shared between two atoms in a molecule. For example; CH₄ F₂, Cl₂, H₂ etc.

 

·         Double Covalent Bond: When two pairs of electrons are shared between two atoms in a molecule. For example; O₂, CO₂ etc.

 

·         Triple Covalent Bond: When three pairs of electrons are shared between two atoms in a molecule. For example; N₂ etc.

Versatile Nature of Carbon: The existence of such a large number of organic compounds is due to the following nature of carbon,

·         Catenation

·         Tetravalent nature.

·         Formation of covalent bond.

(i) Catenation: The self linking property of an element mainly carbon atom through covalent bonds to form long straight, branched and rings of different sizes are called Catenation.
This property is due to

·         The small size of the carbon atom.

·         The great strength of the carbon-carbon bond.

Carbon can also form stable multiple bonds (double or triple) with itself and with the atoms of other elements.

Straight Chain:

Branched Chain

Rings

(ii) Tetravalent Nature: Carbon has valency of four. It is capable of bonding with four other atoms with single covalent bond as well as double or triple bond.

(iii)  Covalent bonds:  Carbon forms covalent bonds

Allotropes of Carbon

– The phenomenon of the existence of the same element in different physical forms with similar chemical properties is known as allotropy.

– Some elements like carbon, sulphur, phosphorus, etc., exhibit this phenomenon.

– Crystalline allotropes of carbon include diamond, graphite and, fullerene.

– Amorphous allotropes of carbon include coal, coke, charcoal, lamp black and gas carbon.

Graphite

·         It is a pure form of carbon.

·         This allotrope of carbon is composed of flat two dimensional layers of carbon atoms which are arranged hexagonally.

·          It is a soft, black and slippery solid.

·         This property of graphite persists because it cleaves easily between the layers.

·         In each layer, each C atom is linked to three C atoms via a C-C covalent bond. Each carbon here is sp2 hybridized. The fourth bond is formed as a pi bond. Since the π-electrons are delocalized, they are mobile and can conduct electricity.

·         Each layer is composed of planar hexagonal rings of carbon atoms

·         Carbon-carbon bond length within the layer is 141.5 picometers.

·         Out of four carbon atoms three forms sigma bonds whereas the fourth carbon forms pi-bond.

·         The layers in graphite are held together by Vander Waal forces.

Properties of Graphite:

• Since the layers are stacked over each other, this carbon allotrope can act as a lubricant.
• It also has metallic lustre which helps in the conduction of electricity. It is a very good conductor of both heat and electricity
• One of the most important properties of graphite is that it is used as a dry lubricant for machines at high temperature where we cannot use oil.
• Graphite is used to make crucibles which have the property that they are inert to dilute acids as well as to alkalis.

·         Has a density of 2.25 g/cc.

Note: In comparison to diamond, Graphite is thermodynamically more stable.

 Structure of Carbon Allotrope (Graphite):

Uses of Graphite

• It is making electrodes.
• It is used as lubricant
• It is mixed with clay or wax to make lead pencils
• It is used to making moderator of nuclear reactor.

 

Diamond

·         It is the purest crystalline allotrope of carbon.

·         It has a number of carbons, linked together tetrahedrally.

·         Each tetrahedral unit consists of carbon bonded to four carbon atoms which are in turn bonded to other carbons. This gives rise to an allotrope of carbon having a three-dimensional arrangement of C-atoms.

·         Each carbon form covalent bonds with four other carbon atoms at the corners of the tetrahedral structure.

·         It is hard because breaking a diamond crystal involves breaking a large number of strong covalent bonds. Breaking covalent bonds is no easy task. This property makes this carbon allotrope the hardest element on earth.

 

Physical Properties of Diamond

• It is extremely hard
• It has a very high melting point
• It has a high relative density
• It is transparent to X-rays
• It has a high value of the refractive index
• It is a bad conductor of electricity
• It is a good conductor of heat
• It is insoluble in all solvents

·         Has a high density of 3.5g/cc.

·         Has a very high refractive index of 2.5.

Uses of Diamond

• It is used as cutting tool.
• It is used in making jewellery.
• It is used in manufacturing of tungsten filament.

FULLERENE

·         Buckminsterfullerene (C60), C70 and buckytube  are allotropes of carbon.

·         The structure of fullerene is like in a cage shape due to which it looks like a football.

·         They are spheroidal molecules having the composition.

·         These carbon allotropes can be prepared by evaporating graphite with a laser.

·         Unlike diamond, fullerenes dissolve in organic solvents. The fullerene C60 is called ‘Buckminster Fullerene’.

There are 12 five-membered rings(pentagon) and 20 six-membered rings(hexagon) in C60 like in a soccer ball.

Uses:

·         Purification of natural gas

·         As lubricant( act as molecular bearing)

·         Behave as super conductor at high temperature.

HYDROCARBONS

Hydrocarbons are organic compounds that are entirely made up of only two kinds of atoms – carbon and hydrogen. Typically, hydrocarbons are colourless gases that have very weak odours.

Classification and Types of Hydrocarbons

Older chemists classified hydrocarbons as either aliphatic or aromatic. The classification was done based on their source and properties. Aliphatic hydrocarbons were derived from chemical degradation of fats or oils whereas aromatic hydrocarbons are the substances that were formed due to chemical degradation of certain plant extracts. However, today we classify hydrocarbons on the basis of structure and not merely on the origin.

Homologous Series:

Series of compounds with same general formula and functional group is known as homologous series. Compounds belonging to the same homologous series show similar properties. Compounds of homologous series differ by CH₂ from their consecutive members. Each subsequent compound in a homologous series differs by 14 au. Example: Alkanes; such as, Methane, Ethane, Propane, Butane, etc. belong to same homologous series.

Series of organic compounds having the same functional group and chemical properties and successive members differ by a CH₂ unit or 14 mass units are known as Homologous series.

Homologous series of Alkanes, Alkenes and Alkynes

1.    Alkanes

The simplest Hydrocarbon is methane, CH₄. This is the simplest member of a series of hydrocarbons. Each successive member of the series has one more Carbon atom than the preceding member. This series of compounds are called alkanes (C_nH_2n+2). The lighter ones are gases and used as fuels.

Following table is used to assign name for parent chain as per the no of carbon atom present:

Number of Carbons	Name
1	meth
2	eth
3	prop
4	but
5	pent
6	Hex
7	Hept
8	Oct
9	Non
10	Dec
11	Undec
12	dodec

Nomenclature of Alkane:

Steps are as follows:-

Find the longest chain of carbons in the molecule. The number of carbons in the longest chain becomes the parent name 

 

2.    Alkenes

Another series of compounds is called the alkenes. These have a general formula: C_nH_2n. Alkenes have fewer hydrogen atoms than the alkanes. The extra valencies left over occur as double bonds between a pair of Carbon atoms. The double bonds are more reactive than single bonds making the alkenes chemically more reactive.

3.    Alkynes

A third series are the alkynes. These have the following formula: C_nH_2n-2.

Alkynes have two carbon atoms joined by a triple bond. This is highly reactive making these compounds unstable.

Rules for Alkene

 1.   The ene suffix (ending) indicates an alkene.

 2.   The longest chain chosen for the root name must include both carbon atoms of the

double bond.

Alkyne Nomenclature

 1.  The yne suffix (ending) indicates an alkyne.
 2.   The longest chain chosen for the root name must include both carbon atoms of the triple bond.

Properties of Compounds of Same Homologous Series

a.    Compounds of same homologous series have same general formula.

b.    Compounds of same homologous series differ from their consecutive members by one carbon atom and two hydrogen atoms, homologous series differ from their consecutive members by one carbon atom and two hydrogen atoms, i.e. by CH₂

c.    Compounds of same homologous series have same chemical properties.

d.    Members of given homologous series have the same functional group.

e.    Compounds of same homologous series differ by molecular mass of 14u from their consecutive members

f.     Compounds of same homologous series differ by physical properties with increase or decrease in molecular mass. 

Isomerism: 

Compounds having the same molecular formula but different structural formula and properties are known as Isomers and this phenomenon is known as Isomerism.

Structural Isomerism: Compounds having the same molecular formula but different structures are called Structural isomers. Example: Isomers of butane (C₄H₁₀)