Question

Of the following, which element has the highest first ionization energy?

Cs At Ra Po

Answer 1

ionization energy is the energy needed to remove valance electron . In a period we know size
of atom decreases from left to right. So valance electron is more tightly held to the nucleus due to
attraction. Then more energy will be required to remove valance electron. Thus from left to right
in a period, ionization energy increases. Also ionization energy decreases down the group .

when we compare metals and non metals in a particular period, non metal have higher I.E.

At belongs to 17 group in 6 th period will have highest ionization energy since all 3 elements
belongs to 6th period. Ra is in 7 th period .But this too has lower ionization energy than other elements

Answer : At
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