Question

which is the ground state electronic configuration of an alkaline earth metal?

a) ( 1 s ^ { 2 } 2 s ^ { 2 } 2 p ^ { 6 } 3 s ^ { 2 } 3 p ^ { 6 } 4 s ^ { 2 } 3 d ^ { 10 } 4 p ^ { 2 } )
b) ( 1 s ^ { 2 } 2 s ^ { 2 } 2 p ^ { 6 } 3 s ^ { 2 } 3 p ^ { 6 } 4 s ^ { 2 } )
c) ( 1 s ^ { 2 } 2 s ^ { 2 } 2 p ^ { 6 } 3 s ^ { 2 } 3 p ^ { 6 } 4 s ^ { 2 } 3 d ^ { 2 } )
d) ( 1 s ^ { 2 } 2 s ^ { 2 } 2 p ^ { 6 } 3 s ^ { 2 } 3 p ^ { 6 } 4 s ^ { 1 } )

Explanation:

Alkaline earth metals are in Group 2 of the periodic table. Their general electron - configuration is \(ns^{2}\), where \(n\) represents the principal quantum number of the outermost shell.

• Option A: The electron - configuration \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{2}\) corresponds to Ge (Germanium), which is a p - block element (\(4p^{2}\) outer - shell electrons).
• Option B: The electron - configuration \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}\) has the outer - shell configuration \(4s^{2}\). If \(n = 4\), the element is Ca (Calcium), which is an alkaline earth metal.
• Option C: The electron - configuration \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{2}\) corresponds to Ti (Titanium), a d - block (transition) element.
• Option D: The electron - configuration \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{1}\) corresponds to K (Potassium), an alkali metal (\(ns^{1}\) outer - shell configuration).

Answer:

B. \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}\)