Question
Mon September 12, 2011 By:

why I.E1 of Be >I.E1 of B but IE2 of Be

Expert Reply
Mon September 12, 2011

I.E1 of Be is larger than the I.E1 of B because the first electron in Be is removed from the completely filled 2s-orbital which is extra stable. Hence more energy is required to remove that electron. The second electron in Be is removed from the half filled 2s orbital while the second electron in B is removed from the completely filled 2s orbital. Therefore I.E2 of Be is smaller than the I.E2 of B.

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