Why and how carbon completes its octet?

ORGANIC CHEMISTRY

SOLVED TEST YOURSELFS

Test Yourself 11.1 (ORGANIC COMPOUNDS)

  1. No. i. Why and how carbon completes its octet?

Answer. Octet rule is Having 8 electrons in the valance shell of an atom. All the elements (atoms) complete their octet to gain stability either losing or gaining electrons or by sharing of electrons.

Carbon atom consists of 4 electrons in its valence shell. It completes its octet by sharing of its 4 electrons with other atoms. So that it gains stability

  1. No. ii. Point out the properties of carbon which are responsible for formation of long chains of carbon atom compounds.

Answer. Property of carbon atom which is responsible for formation of long chains of carbon atom compounds is catenation. It is ability of carbon atoms to link with other carbon atoms to form long chains and large rings. Carbon atom fulfils the two basic conditions to exhibit catenation.

(a)      It has valence greater than two.

(b)      It forms stronger bonds with its own atoms than that of its bonds with other atoms especially oxygen.

For example, both silicon and carbon have similar electronic configurations but carbon shows catenation whereas silicon does not. It is mainly due to the reason that C-C bonds are much stronger (355 kJ mol-1) than Si-Si (200 kJ mol-1) bonds. On the other hand, Si-O bonds are much stronger (452 kJ mo-1) than C-O bonds (351 kJ mol-1). Hence, silicon occurs in the form of silica and silicates in nature.

  1. No. iii. Why the melting and boiling points of organic compounds are low.

Answer. Melting point of a compound depends upon the nature of the bonding of the compound. Compounds having covalent bonding have low melting points than that of compounds having ionic bonding in them. As organic compounds consists of covalent bonding their melting point are low.

Boiling point depends upon intermolecular forces between the molecules. Organic compounds are mostly non-polar or slightly polar, Intermolecular forces between the organic compounds are London forces of attraction. Because of these weak forces boiling points of organic compounds are low.

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