Here's why:

* Atomic Number: The atomic number of an element is the number of protons in its nucleus. Since atoms are electrically neutral, they also have an equal number of electrons.

* Nitrogen's Atomic Number: Nitrogen's atomic number is 7, meaning it has 7 protons and therefore 7 electrons.

To put it simply, the number of protons in an atom determines its identity (what element it is), and the number of electrons must match the number of protons to keep the atom neutral.