Three isotopes of chromium are chromium-50, chromium-52, and chromium-53. how many neutrons are in each isotope, given that chromium has an atomic number of 24?

chromium-50 has 26 neutrons
chromium-52 has 28 neutrons
chromium-53 has 29 neutrons
You subtract the total mass of the isotope (so lets use chromium-50), which, since each proton and neutron weights about 1 atomic mass unit, is the total of protons and neutrons. So subtract the the atomic number (which is the total number of protons chromium will always have, 24) from the mass, 50 - 24 to get a remaining 26, which must be neutrons

The problem here is that according to aufbau principle before 3d orbital 4s subshell comes.after filling 3p orbital with electrons you have 4 electrons left, you place two in 4s with opposite spin and the other two in 3d in any of its two orbitals of total five orbitals with the same spin.

The net force is 100