# If an atom has an atomic number of 10, how many electrons does it have?

##### 1 Answer
Oct 30, 2015

$10$ Unless of course, the atom has a charge in it.

#### Explanation:

You just have to remember these basic rules:

(1) The atomic number is equal to the number of protons in that atom.

(2) If the atom is neutrally charged (or zero charged), the number of electrons is the same as the number of protons.

Otherwise, negative charge means that the atom gained electrons, and for positive charge the atom lost electrons.

For example,

$N a$ (atomic number = 11) : $1 {s}^{2}$ $2 {s}^{2}$ $2 {p}^{6}$ $\textcolor{red}{3 {s}^{1}}$ (ground state)

$N {a}^{\text{+1}}$(atomic number = 11) : $1 {s}^{2}$ $2 {s}^{2}$ $\textcolor{b l u e}{2 {p}^{6}}$ (lost 1 ${e}^{-}$)

$C l$ (atomic number = 17) : $1 {s}^{2}$ $2 {s}^{2}$ $2 {p}^{6}$ $3 {s}^{2}$ $\textcolor{red}{3 {p}^{5}}$ (ground state)

$C {l}^{\text{-1}}$ (atomic number = 17) : $1 {s}^{2}$ $2 {s}^{2}$ $2 {p}^{6}$ $3 {s}^{2}$ $\textcolor{red}{3 {p}^{6}}$ (gain 1 ${e}^{-}$)