Question

Six elements A, B, C, D, E and F have the following atomic numbers (A = 12, B = 17, C = 18, D = 7, E = 9 and F = 11). Among these elements, which element has the highest ionisation potential and also belongs to the $3^{rd}$ period?

• A. D
• B. B
• C. C
• D. F

Answer 1

The correct option is C C

Electron configuration of A = 2,8,2
Electron configuration of B = 2,8,7
Electron configuration of C = 2,8,8
Electron configuration of D = 2,5
Electron configuration of E = 2,7
Electron configuration of F = 2,8,1
In this we can see that the octet of element C is complete 2, 8, 8 i.e. it has noble gas configuration and it is the most stable of all. Ionization energyis the energyrequired to remove the most loosely held electron from one mole of gaseous atoms to produce 1 mole of gaseous ions. Out of all these it is very difficult to remove electron from element C, the element which has maximum stability so it has maximum ionization energy.