When a calcium atom becomes an ion?

It looses 2 electrons, when ions come together to form and ionic bond they always join in numbers that cancel out the positive and negative charges .

  -hope this have helped you well .

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.

Answer246 k;