Answer
A nitrogen atom possesses 5 valence electrons.
Work Step by Step
We would take the number of valence electrons to be the number of electrons in the outermost occupied shell, since in most cases, the electrons taking part in chemical bonding are those in the outermost shell.
The number of electrons in the outermost occupied shell is shown by the group number in the periodic table, so the number of valence electrons of an element equals its group number.
$N$ belongs to group 5A. So, a nitrogen atom possesses 5 valence electrons.
