Answer:
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
