Question

Which of the following order(s) for electron affinity is/are correct?
(a)- S > O < Se
(b)- Cl > F
(c)- S > O
(d)- O > S
(e)- N > P
(f)- C > N
(A)- a, b, c, e
(B)- a, b, c, f
(C)- b, c, d, e
(D)- b, c, f

Answer 1

Hint: As we move from left to right in the period the electron affinity becomes more negative while the strength of electron affinity increases and as we move down the group the electron affinity becomes less negative which means the strength of electron affinity decreases.

Complete answer:
Electron affinity is characterized as the energy shift (in kJ/mol) of the gaseous atom, where a negative ion is attached to the atom. That is, the probability of an electron acquiring the neutral atom. As we move from left to right in the period the electron affinity becomes more negative and as we move down the group the electron affinity becomes less negative.
(a)- S > O < Se
This is correct because oxygen is the first atom for its group while sulfur is the second and selenium is the third. Both of them have less negative electron affinity than oxygen.
(b)- Cl > F
This is correct because in fluorine there are interelectronic repulsions due to which its electron affinity decreases than chlorine.
(c)- S > O
This is correct because in oxygen there are interelectronic repulsions due to which its electron affinity decreases than sulfur.
(d)- O > S
This is wrong because sulfur has a higher electron affinity.
(e)- N > P
This is wrong because nitrogen has an exceptional case in electron affinity. As we know that nitrogen has a half-filled p-orbital due to which extra stability is present. Due to this extra stability, the electron affinity of nitrogen is positive.
(f)- C > N
This is correct due to the positive electron affinity of nitrogen.

Therefore, the correct answer is an option (B)- a, b, c, f

Note:
Normally the electron affinity values for the non-metals are negative because when the electron is added to the neutral atom then the energy is released but when we have to add the energy then some of the non-metals have positive electron affinity.