Competency #6
Answer and Explanation
The size of the atoms increases as you go down a group.
This is because, as you go down a group, the electrons are being added to larger and larger shells. For example, in sodium (Na) the valence electron is in the third shell, while in potassium (K) the valence electron is in the forth shell.
Note: Valence electrons are the electrons in the outer-most shell.
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