# How many unpaired electrons are in a N atom?

Oct 18, 2016

Well, nitrogen's atomic number is $7$, so it has $5$ valence electrons (two in the $2 s$ orbital and three in the $2 p$ orbitals) and $2$ core electrons (two in the $1 s$ orbital).

For simple atoms, filling electrons goes in accordance with:

• The Aufbau principle (lowest to highest energy ordering)
• Hund's rule (one electron per orbital first, then pair them up after all orbitals for a single energy level are singly occupied)
• The Pauli Exclusion Principle (opposite spins on the two electrons in each orbital, if there are two; otherwise spin up is the common convention).

Thus, the orbital configuration is (energy increases as you go upwards on this scale):

$\underline{\uparrow \textcolor{w h i t e}{\downarrow}} \text{ " ul(uarr color(white)(darr)) " } \underline{\uparrow \textcolor{w h i t e}{\downarrow}}$
$\underbrace{\text{ "" "" "" "" "" "" "" }}$
$\text{ "" ""2p orbitals}$

$\underline{\uparrow \downarrow}$
$\text{ 2s}$

$\underline{\uparrow \downarrow}$
$\text{ 1s}$

Based on this diagram, how many electrons are unpaired?