Question

The first ionisation potential of `Na,Mg,Al` and `Si` are in the order
A. `NaltMg gtAlltSi`
B. `NagtMggtAlgtSi`
C. `NaltMgltAlltSi`
D. `NagtMggtAlltSi`

Answer 1

Correct Answer - A
`IE_(1)` of Mg is higher than that of Na because of increased nuclear charge and also that of Al because in Mg a 3s-electron has to be removed while in Al it is the 3p-electron. The `IE_(1)` of Si is, however, higher than those of Mg and Al because of it increased nuclear charge. Thus, the overall order is `NaltMg gtAl ltsi`.