Question

How many protons and electrons are present in $C{a}^{2+}$ ion ?

• A. $20$ protons; $20$ electrons
• B. $20$ protons; $22$ electrons
• C. $18$ protons; $18$ electrons
• D. $20$ protons; $18$ electrons

Answer 1

The correct option is D $20$ protons; $18$ electrons

The atomic number of $Ca$ is $20.$ Thus, it contains $20$ protons and $20$ electrons.
One $Ca$ atom loses $2$ electrons to form $C{a}^{2+}$ ion.
$Ca\to C{a}^{2+}+2e^{-}$
Hence, the number of electrons in $C{a}^{2+}$ ion is $20-2=18$.
Thus, $20$ protons and$18$ electrons are present in $C{a}^{2+}$.