Name three elements that have a single electron 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 a single electron in their outermost electron are Lithium ($\mathrm{Li}$), Sodium ($\mathrm{Na}$), and Potassium ($\mathrm{K}$).
  • Electronic configuration of $\mathrm{Li}$ = $1{\mathrm{s}}^{2}2{\mathrm{s}}^1$
  • Electronic configuration of $\mathrm{Na}$ = $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^1$
  • Electronic configuration of $\mathrm{K}$ = $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}4{\mathrm{s}}^1$
• Sodium is located in group 1, which means that it has one valence electron. This valence electron is located in Sodium's third energy shell.

• Similarly in the case of lithium, sodium and potassium, etc.