Classification

For second ionisation potential, electron will have to be removed from valence shell of the following ions: In general, ionisation energy increases from left to right in a period. However, exception occur between adjacent atoms in a period, greater amount energy is required for removal of electron from completely half-filled or completely filled orbital than the same for adjacent atom with either less than completely half-filled or less than completely filled orbital. Therefore, ionisation potential of is greater than that of F+. Also ionisation potential of is greater than but less than
both (periodic trend). Hence, overall order is 2nd IP : O > F > N > C.

Atomic radius of noble gases are greater than halogens of same period, hence (a) is the correct answer.

Ionisation energy increases from left to right in a period. However, exception occur between group 2 and group 13 elements on account of stability of electronic configuration of valence shell. The desired order is Na < Mg > A1 < Si

Among isoelectronic species, the relation in size is cation < neutral < anion Hence, has smallest size.

has highest ionization energy (half-filled)

Pb has most stable +2 oxidation state due to inert pair effect.

(a) is the correct order of size due to lower positive charge on .
(b) : Isotopes with same charge have same size because isotopes differ in compositions of nuclei which
do not affect the atomic/ionic radius.
(c) is the correct order. Among isoelectronic species, anion has greater size than cation.
(d) is the correct order. For the same elements, lower the positive charge, larger the ions

is the least stable ion. has stable electronic configuration, addition of electron decreases stability.