Physiology/Medicine: Why are these ions more concentrated in these areas

Physiology/Medicine: Why are these ions more concentrated in these areas?
These ions, Ca2+, Na+, Cl-, and K+.

K+ is 50 times more concentrated in intracellular fluids (ICF) than interstitial fluids (ECF)
Na+ is 12 times more concentrated in ECF than ICF.

My question is, why does this accumulation of ions in specific areas occur? Following digestion, these ions are absorbed into the bloodstream. There are sodium/potassium pumps but can it alone be responsible for this accumulation?

Yes, the Na+/K+ pumps are pretty much responsible for this build up of concentration on either side of the cell membrane. I think I've read that 1/3 of your body's ATP goes to these pumps to keep the concentration as they are. This allows for an electrochemical gradient that stabilizes each cell and helps with neuronal action potentials.

It might be to do with the amount of electrons in a Sodium or calcium atom during ionization.