Question

Which one of the following arrangements represents the
correct order of least negative to most negative electron gain
enthalpy for C, Ca, Al, F and O? [NEET Kar. 2013]
(a) Ca < Al < C < O < F
(b) Al < Ca < O < C < F
(c) Al < O < C < Ca < F
(d) C < F < O < Al < Ca

Answer 1

Option A

• Among all the options given, in the first option the arrangements represent the correct of least negative to most negative electron gain enthalpy  for the given.

Answer 2

Let us arrange them

Explanation:

Electron gain enthalpy

It is the energy changes that occur  when an electron is added to outermost shell of an atom .

This energy is always released but in some cases ,where there is no attraction for incoming electron then it is positive in that case .

Let us arrange them in correct order from least negative to most negative electron enthalpy :

(a) Ca < Al < C < O < F

In case of fluorine , the incoming electron is attracted due to its small size and high nuclear charge .

As the size increases attraction for incoming electron goes on decreasing .

Therefore , this order is observed .