Elements in the same group/family of the periodic table are similar in what way?

Elements in the same group in the periodic table have similar chemical properties. This is because their atoms have the same number of electrons in the highest occupied energy level. Group 1 elements are reactive metals called the alkali metals.Group 0 elements are unreactive non-metals called the noble gases.

What does that mean you dum bum

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.