Only 14 one please

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.

Mg-26 and mg-24 are pair of isotopes. isotopes are defined as atoms of the same element having same atomic number but different mass number. i hope that was .