Question

Which of the following is/are wrong statement (s) ?

• A. The second Ionization potential is always less than the first Ionization potential of an atom
• B. If the addition of an electron to an ion leads to complete octet, then the process is always exothermic
• C. Chlorine has highest electronegativity
• D. First Ionization potential of $N$ is higher than first ionization potential of $F$, because $N$ has half filled subshell

Answer 1

Answer: (A), (B), (C), (D)

The correct options are
A The second Ionization potential is always less than the first Ionization potential of an atom
B If the addition of an electron to an ion leads to complete octet, then the process is always exothermic
C Chlorine has highest electronegativity
D First Ionization potential of $N$ is higher than first ionization potential of $F$, because $N$ has half filled subshell

(a) $I{E}_2>I{E}_1$ (as ENC increases)
Second ionization energy is greater than first ionization energy because effective nuclear charge increases after removal of one electron from any atom. Hence, the electrostatic force increases and removal of second electron becomes tough.
(b)
$O^{-}+e^{-}\to O^{2-}$
Due to force of repulsion between $O^{-}$ and $e^{-}$ the process is endothermic.
For addition of electron to an anion, energy is supplied as electron -electron repulsion is more and there is a potential barrier which is needed to be crossed for the completion of octet or for addition of further electron. Hence, the process is endothermic. For example the second electron affinity of oxygen is positive means that the process of addition of an electron to $O^{-}$ before completion of octet is endothermic.

(c) Flourine has highest electronegativity in the periodic table.

(d) First ionization potential of $N$ is less than first ionization potenital of $F$ because of small size of $F$ and higher effective nuclear charge.