Elements forming ionic compounds attain noble gas configuration by either gaining or losing electrons from their outermost shells. Give reason to explain why carbon cannot attain noble gas configuration in this manner to form its compounds. Name the type of bonds formed in ionic compounds and in the compounds formed by carbon. Also give reason why carbon compounds are generally poor conductors of electricity.

OR


i. State the meaning of functional group in a carbon compound. Write the functional group present in (a) ethanol and (b) ethanoic acid and also draw their structures.


ii. Write the name and general formula of a chain of hydrocarbons in which an addition reaction with hydrogen can take place. Stating the essential conditions required for an additional reaction to occur write the chemical equation giving the name of the reactant and the product of such a reaction.

Ionic bonds are formed between dissimilar atoms by transfer of electrons. The number of electrons gained or lost is to achieve stable noble gas configuration. The atomic number of carbon is 6. It has 4 electrons in its outermost shell (Electronic configuration: 2,4) hence would need 4 more electrons to attain stable noble gas electronic configuration.


If it would have given four electrons, C4+ cation would have been formed but this is not possible as the removal of four valence electrons requires a huge amount of energy, leaving behind six protons in the nucleus of the carbon cation. This would make it highly unstable.


If it would have taken four electrons, Carbon would have formed C4− anion, but it is difficult for its nucleus to hold 6 protons and 10 electrons. Hence this is also not feasible.


Thus, carbon achieves stable noble gas electronic configuration by sharing its four valence electrons forming covalent compounds by covalent bonding. (Covalent bonding: Bond formed by sharing electron pairs between atoms with low electronegativity difference or almost same electronegativity).


The type of bonds formed in ionic compounds is ionic bond and in the compounds formed by carbon is covalent bond.


Carbon compounds are bad conductors of electricity because they are covalent compounds formed by covalent bonding. They lack free electrons needed for conduction of electricity.


OR


i) Functional group in a carbon compound: Groups attached or bonded to a carbon atom in a carbon compound that defines the chemical property of the compound is called a functional group.


The functional group present in:


a) Ethanol (C2H5OH): (Hydroxy group: -OH group)- Alcoholic group


Structure:


ethanol.PNG


b) Ethanoic acid (CH3COOH): (Carboxyl group: -COOH) - Carboxylic acid.


Structure:



ii. Name and general formula of a chain of hydrocarbons in which an addition reaction with hydrogen can take place are:


i) Alkene: (CnH2n)


ii) Alkyne: (CnH2n-2)


Essential conditions for an additional reaction to occur are:


a) Multiple bonds must be present between the carbon atoms for addition reactions to take place.


b) Catalysts are required for addition of hydrogen or other halogens or atoms to the reaction.


Chemical equation of such a reaction:


CH2=CH2 + H2 -> CH3 + CH3 (in presence of catalyst like platinum or nickel)


where CH2=CH2 is ethene (reactant), H2 is hydrogen and CH3-CH3 is ethane (product).


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