Which atom in the ground state has the same electron configuration as a calcium ion, $Ca^(2+)$ in the ground state?

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Answer 1 · 2016-04-19T16:40:22

The preceding Noble Gas.

Calcium, $Z=20$ , has 20 electrons as the neutral atom. $Ca^(2+)$ necessarily has 18 electrons. The preceding Noble $Z=20-2=18$ is argon, $Ar$ .

Which atom in the ground state has the same electron configuration as a calcium ion, Ca^(2+)Ca^(2+) in the ground state?