What atom has 8 protons and 10 electrons?

In your case, you have 8 protons and 10 electrons. This means that the atom will carry a total 2 xx (1-) = 2- net charge. Therefore, you are dealing with an anion that carries a 2- net charge, i.e. it has two more electrons than it does protons.

not clear

the atomic number will stay the same no matter how many electrons it has, so it doesn’t decrease nor increase. it’ll only change with a different number of protons