# What are the four quantum numbers for the last electron in Fe^(3+)?

Sep 14, 2017

For iron, $Z = 26$.......

#### Explanation:

And so we would write the following electronic configuration with respect to the atom....

$1 {s}^{2} 2 {s}^{2} 2 {p}^{6} 3 {s}^{2} 3 {p}^{6} 4 {s}^{2} 3 {d}^{6}$

But upon oxidation.......we gets $F {e}^{3 +}$, and the standard electronic configuration is.....
${\left\{1 {s}^{2} 2 {s}^{2} 2 {p}^{6} 3 {s}^{2} 3 {p}^{6} 3 {d}^{5}\right\}}^{3 +}$

So the last electron is from one of the (degenerate!) $\text{d-orbitals....}$

And thus...........

n=3; l=2 "(i.e. we have d-orbitals with 2 nodal planes)";m_l=-2,-1,0,1,or2; m_s=+-1/2#