Question

the electron configuration of calcium is $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}$. in its reactions, calcium tends to form the $ca^{2+}$ ion. which electrons are lost upon ionization?
all of the 4s electrons
the 1s electrons
all of the 3s electrons
two of the 3p electrons

Explanation:

When an atom ionizes, it loses electrons from the outermost (highest - energy) shell first. For calcium with electron configuration \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}\), the outermost shell is the 4s shell. Since \(Ca^{2 +}\) has a + 2 charge, it loses 2 electrons. These 2 electrons come from the outermost 4s orbital. The 1s electrons are in the innermost shell and are tightly bound. The 3s and 3p electrons are in lower - energy shells compared to 4s (in terms of ionization for main - group metals like calcium).

Answer:

all of the 4s electrons