Question

What happens to atomic size when we go from left to right in a period and top to bottom in a group? Give reason?

Answer 1

In a period, the atomic size decreases from moving left to right. This is due to an increase in nuclear charge which tends to pull the electrons closer to the nucleus and reduces the size of the atom.

In a group, the atomic size increases from top to bottom. This is because new shells are being added as we go down the group. This increases the distance between the outermost electrons and the nucleus so that the atomic size increases in spite of the increase in nuclear charge.

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