Question 102

A ground-state main-group atom is located in period 4. In the school shell model, what does the period number indicate?

The atom has four occupied principal shells.Correct answer
The atom has four protons.
The atom must have four valence electrons.
The atom belongs to group 4.

Explanation

For a ground-state main-group atom, period 4 indicates four occupied principal electron shells. It does not mean four protons or necessarily four valence electrons, because those quantities are determined by different features.

Explanation

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