Question

the third period contains only 8 electrons even though the electronic capacity of the third shell is 18 give scientific reason

Answer 1

this happens because valence shell can't consists more than 8 electrons

Answer 2

The third shell has the capacity to accommodate 18 electrons. However, after the third shell receives 8 electrons, the filling of forth shell begins. This is because the outermost shell does not havecapacity to hold more than 8 electrons. Therefore, third period has only 8elements