Question

select the correct statement(s) about an electrically neutral atom of argon (ar).
it has 3 electron shells (energy levels).
it has 2 valence electrons.
it has 18 total electrons.
it has 8 electron shells (energy levels).
it has 18 valence electrons.
it has 8 valence electrons.
it has 18 protons and an atomic number of 18.

Explanation:

• For an electrically neutral atom, the number of electrons equals the number of protons. Argon has an atomic number of 18, so it has 18 protons and 18 electrons.
• The electron configuration of argon is \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}\). It has 3 electron shells (energy levels).
• The valence electrons are the electrons in the outermost shell. For argon, the outermost shell (\(n = 3\)) has \(2 + 6=8\) valence electrons.

Answer:

• It has 3 electron shells (energy levels).
• It has 18 total electrons.
• It has 8 valence electrons.
• It has 18 protons and an atomic number of 18.