Question

Lewis postulated that atoms achieve the stable octet(or duplet in case of H and He) when they are

joined through chemical bonds or in other words atoms join together either by transfer of valence

electrons from one atom to another (gaining or losing) or by sharing of valence electrons in order to

complete their octet (i.e. eight electrons in the valence shell). This is known as octet rule. Octet rule has

not been followed in all molecules.

Elements of the third and higher periods of the periodic table, because of the availability of d-orbitals

can expand their covalency and can accommodate more than eight valence electrons around the central

atom. This is referred as expanded octet

Here, also the octet rule is not applicable. e.g. PF5, (10 electrons around P-atom), SF6 (12 electrons

around S-atom), H2SO4 (12 electron around S atom). Compound having expanded octet are also termed

as hypervalent compounds.

Formal charge is a factor which is based on pure covalent view of bonding in which electron pairs are

shared equally by neighbouring atom. It may be defined as the difference between the number of

valence electrons of that atom in an isolated or free state and the number of electrons assigned to that

atom in the Lewis structure. It is represented as:

FC= V-L-1/2 S

where, FC= formal charge on an atom in a Lewis structure, V = total number of valence electrons in the

free atom, L = total number of non-bonding (lone pair) electrons and S= total number of bonding

(shared) electrons.

In these questions (i-iv) a statement of Assertion followed by a statement of Reason is given. Choose

the correct answer out of the following choices :

(a) Assertion and Reason both are correct statements and Reason is correct explanation for Assertion.

(b) Assertion and Reason both are correct statements but Reason is not correct explanation for

Assertion.

(c) Assertion is correct statement but Reason is incorrect statement.

(d) Assertion is incorrect statement but Reason is correct statement.

(i) Assertion: In case of polyatomic ions, the net charge is possessed by the ion as a whole and not by a

particular atom.

Reason: The formal charge of an atom in a polyatomic molecule or ion may be defined as the

difference between the number of valence electrons of that atom in an isolated or free state and the

number of electrons assigned to that atom in the Lewis structure.​

Answer 1

Answer:

the structural and functional unit of living organisms is called cell