if the atom has 4 electrons in ground state, how many electrons are located in each orbital?

Answer 1

None!!!!

I dare you to prove me right or wrong.
Sorry! Just wanted to grab your attention.
Quantum mechanics (the basis of the orbital model)
is based on probability zones.
Except for the exceptions. Look up "back bonding".
So these are probabilities, not absolutes.
Btw the reason for two e's in each zone is their
"spin state". Funny how spin can be coupled at
radio frequencies, yet electrons coupled at visible light
frequencies.
OK 1s,2s

Answer 2

2 in the 1s orbital, 2 in the 2s orbital.