In the fourth period of the periodic table, how many elements have one or more 4p electrons

The fourth period, or fourth row, of the periodic table contains the elements from Z = 19 (potassium) to Z = 36 (kripton).

The abbreviated electron configuratin of potassium is K = [Ar] 4s.

Where [Ar] is 1s2 2s2 2p6 3s2 3p6.

The next element, Calcium, Z = 20, has electron configuration Ca = [Ar] 4s2.

Starting the next element, Scandium, Z = 21, the atoms start to fill the 3d  orbitals. Scandium has electron configuration Sc = [Ar] 4s2 3d.

The 3d orbitals permit to accomodate 10 electrons. So, the filling of 3d orbitals end with the element Z = 30, wich is zinc. The electron configuration of zinc is Zn =[Ar] 4s2 3d10.

So, starting with the element Z = 31 (gallium) until Z = 36, this is 6 elements, will fill the 4p orbitals.Those are Ga, Ge, As, Se, Br and Kr.

The answer is that six elements in the fourth period of the periodic table have one or more 4p electrons. You can find those elements in the right side of the period and are from 13 group to 18 group.