KVPY2020ChemistryClassification of Elements and Periodicity in Properties
The first ionization potential IP of the elements Na , Mg , Si , P , Cl and Ar are 5 . 14 , 7 . 65 , 8 . 15   10 . 49 , 12 . 97 and 15 . 76   eV , respectively. The IP (in eV ) of K is closest to :
Options
- A13 . 3
- B18 . 2
- C4 . 3
- D6 . 4
Correct answer
C. 4 . 3
Step-by-step solution
The ionisation energy decreases down the group. Hence, the first ionisation potential of K is less than Na . The first ionisation potential of sodium is given as 5.14 eV. ∴ The first ionization potential of K is closest to 4 . 3