# How do you write the electron configuration of scandium?

$S c , Z = 21$
$1 {s}^{2} 2 {s}^{2} 2 {p}^{6} 3 {s}^{2} 3 {p}^{6} 4 {s}^{2} 3 {d}^{1}$
We account for 21 electrons. The valence orbitals may have different ordering (i.e. $3 {d}^{1} 4 {s}^{2}$) but this really doesn't matter so much. Scandium metal commonly forms $S {c}^{3 +}$ ions.