Chemistry
Give reasons for the following:
Atomic size decreases across a period but increases down a group of the periodic table.
Periodic Table
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Answer
Across a period from left to right, nuclear charge increases. This decreases the size of the atom because the electrons are then attracted towards the nucleus with a greater force thereby bringing the outermost shell closer to the nucleus.
Down a group, the number of shells and nuclear charge both increase. But increase in the number of shells dominate over increase in nuclear charge. This increase in the number of shells increases the size of an atom because the distance between the outermost shell and the nucleus increases.
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