Question

Atomic size of group 18 elements is more than the aize of group 17 elements. Why?

Answer 1

Electronic configuration of element 17 -2,8,7

Electronic configuration of element 18-2,8,8

Since the group 17 element has 7 electron in its valence shell the force of attraction between the valence electrons and the nucleus(Nuclear Charge) increase hence the size of the atom decrease whereas in the element of group 18 has a complete duplet configuration due to more number of electons in the valence shells a force of repulsion acts among the electrons which tends to increase the atomic size of the element.

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