Question

How many unpaired electrons are in a N atom?

Answer 1

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

`ul(uarr color(white)(darr)) " " ul(uarr color(white)(darr)) " " ul(uarr color(white)(darr))`
`underbrace(" "" "" "" "" "" "" "" ")`
`" "" ""2p orbitals"`

`ul(uarr darr)`
`" 2s"`

`ul(uarr darr)`
`" 1s"`

Based on this diagram, how many electrons are unpaired?