Calcium is a transition element present in the D block of the periodic table. Calcium has atomic number 20. So its electronic configuration is 2, 8, 8, 2 by the Afbau rule. 2, 8,8 and 2 electrons are present in K,L, M and N shells of the atom. So, we can say that the number of electrons in the third energy level of a calcium atom are 8.
