Which of the following atoms ha the highest first ionisation energy-

1.	Which of the following atoms ha the highest first ionisation energy-
Answer» Rb Na K Sc Solution :Alkali metals of group-1 can REMOVE 1 electron to achieve the STABLE noble gas configuration. Hence they have comparatively low ioinisation. Hence they have comparatively low IONISATION ENERGY. However `Sc([Ar]d^(1)4s^(2))` cannot achieve such stabilisation by removing only 1 electron. therefore it has higher ionisation energy.

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