Which one of the following has lowest ionisation energy-

1.	Which one of the following has lowest ionisation energy-
Answer» `1s^(2)2s^(2)2p^(6)` `1s^(2)2s^(2)2p^(6)3s^(1)` `1s^(2)2s^(2)2p^(5)` `1s^(2)2s^(2)2p^(3)` Solution :The electronic configuration `1s^(2)2s^(2)2p^(6)3s^(1)` is that of an alkali metal. In a certain period of the PERIODIC table, ionisation potential of alkali METALS is the lowest.

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