On moving from left to right in a period in the periodic table, the size of the atom.

1. increases
2. decreases
3. does not change appreciably
4. first decreases and then increases

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Correct answer: (b) decreases

Explanation: On moving from left to right in a period of the periodic table, the atomic number of elements increases. The size of the atom decreases on moving from left to right in a period of the periodic table.