Question

The first\((\triangle_ iH_1)\) and the second \((\triangle_iH)\) ionization enthalpies (in \(kJ\; mol ^{-1}\) ) and the \((\triangle_{eg}H)\) electron gain enthalpy (in \(kJ \;mol^{ -1}\) ) of a few elements are given below: 
Elements                       \(\triangle_iH\)                \(\triangle_iH\)                \(\triangle_{eg}H\) 
   I                                    520                   7300                    -60 
  II                                    419                   3051                    -48 
  III                                  1681                  3374                    -328  
  IV                                  1008                 1846                    -295 
  V                                   2372                  5251                   +48 
  VI                                  738                    1451                    -40
Which of the above elements is likely to be : 

1. the least reactive element.
2. the most reactive metal.
3. the most reactive non-metal.

Answer 1

To identify the nature and reactivity of elements, we compare ionization enthalpy and electron gain enthalpy values.

Low ionization enthalpy indicates metallic and high reactivity. Very high ionization enthalpy and positive electron gain enthalpy indicate least reactivity. Highly negative electron gain enthalpy indicates strong non metallic character.

The least reactive element is Element V. It has very high first and second ionization enthalpy and a positive electron gain enthalpy. This indicates a stable electronic configuration similar to noble gases.

The most reactive metal is Element II. It has the lowest first ionization enthalpy among all the elements, which means it can lose electrons most easily.

The most reactive non metal is Element III. It has a very high ionization enthalpy and the most negative electron gain enthalpy, showing a strong tendency to gain electrons.

Final answers.

Least reactive element is V.

Most reactive metal is II.

Most reactive non metal is III.