Name two elements that have two electrons in their outermost shells.

Valence electrons:

• The valence shell of an atom is its outermost orbital shell.
• These electrons participate in the bonding of other atoms.
• Valence electrons are electrons that are not filled in the outer shells.
• The elements with two electrons in their outermost electron are Magnesium ($\mathrm{Mg}$), Calcium ($\mathrm{Ca}$)
• Magnesium is alkaline earth metal and belongs to group $\mathrm{IIA}$ of the periodic table. It has two valence electrons which are present in $3\mathrm{s}$subshell.
• Electronic configuration of $\mathrm{Mg}$ = $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^2$

• Similarly in the case of Calcium as there are two valence electrons in the outermost shell. So, the number of valence electrons in Calcium is two.
• Electronic configuration of $\mathrm{Ca}$ = $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}4{\mathrm{s}}^2$.