Question

which metalloid has three valence electrons?
boron
arsenic
silicon
lithium

Explanation:

• Boron (\(B\)) is a metalloid. Its electron configuration is \(1s^{2}2s^{2}2p^{1}\). The valence electrons are in the \(n = 2\) shell. The number of valence electrons is \(2 + 1=3\).
• Arsenic (\(As\)) has an electron configuration of \([Ar]3d^{10}4s^{2}4p^{3}\). The number of valence electrons is \(2 + 3 = 5\).
• Silicon (\(Si\)) has an electron configuration of \([Ne]3s^{2}3p^{2}\). The number of valence electrons is \(2+2 = 4\).
• Lithium (\(Li\)) is a metal, not a metalloid. Its electron configuration is \(1s^{2}2s^{1}\), and it has 1 valence electron.

Answer:

boron