Which atom in the ground state has a stable valence electron configuration?
(1) ar (2) al (3) si (4) na

(1) Ar

Explanation: Argon is an element with atomic number of 18. Thus it contains 18 electrons. It's electronic configuration in ground state is:

As argon contains completely filled orbitals, it is stable and is a inert element.

Aluminium is an element with atomic number of 13. Thus it contains 13 electrons. It's electronic configuration in ground state is:

Silicon is an element with atomic number of 14. Thus it contains 14 electrons. It's electronic configuration in ground state is:

Sodium is an element with atomic number of 11. Thus it contains 11 electrons. It's electronic configuration in ground state is:

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