Among halogens, the correct order of amount of energy released in electron gain (electron gain enthalpy) is:

The correct order of increasing electron gain enthalpy with a negative sign for the elements O, S, F, and Cl is : 

1. Cl < F < S < O                   

2. O < S < F < Cl

3. F < S < O < Cl                   

4. S < O < Cl < F

The incorrect match among the following is:

1. B < C < N < O (increasing first ionisation enthalpy)

2. I < Br < F < Cl (increasing electron gain enthalpy)

3. Li < Na < K < Rb (increasing metallic radius)

4. Al³⁺ < Mg²⁺ < Na⁺ <F^- (increasing ionic size)

An element with higher negative electron gain enthalpy in the given pair is:

(i) O or F  (ii) F or Cl
1. O, Cl
2. F, F
3. O, F
4. F, Cl  

Element of the third period that is expected to exhibit positive electron gain enthalpy is: 

The group of metals having the positive value of electron gain enthalpy is:

The basic difference between the  electron gain enthalpy (E_a) and electronegativity (E_N) is: