As you add electrons to an energy level, without adding more protons are there more or less repulsive
forces between the electrons?

There will be more repulsive force between the electrons.

Explanation:

Electrons contain negative charge.As a result the electron will repulse another adjacent negatively charged electron.

   According to the given question addition of electrons to en energy level without adding more protons will increase the overall negative charge in the the energy level in which the electrons are added.

  This ultimately leads to generate more repulsive force between the electrons.

atomic mass = 39

number of neutrons = 20

number of protons= 19

electronic configuration = 1s2 2s2 2p6 3s2 3p6 4s1

the number of electron in first shell = 2

number of electrons in n=3 shell = 8