# How many protons, neutrons, and electrons are in ""_19^39 K^(+)?

Jun 16, 2018

19 protons, 20 neutrons and 18 electrons.

#### Explanation:

The atomic number gives the number of protons 19

$p = 19$

The atomic mass is the sum of the protons and neutrons

$p + n = 39$ $p = 19$

put p into the equation and solve for n the neutrons.

$19 + n = 39$ Subtract 19 from both sides

$19 - 19 + n = 39 - 19$

$n = 20$

The number of electrons equals the number of protons in a neutral atom. The positive charge equals the negative charge. The negative charge is the number of electrons. This ion has a charge of +1. So solve for the negative charge.

$- 19 + 1 = - 18$

The negative charge is -18 so

$e = 18$