Question

State the following: a) Aufbau principle, b) Hund's rule of maximum multiplicity c) Heisenberg Uncertainty principle.

The quantum numbers of six electrons are given below. Arrange them in order of increasing energies. List if any of these combination(s) has/have the same energy (i) n = 4, l = 2, ml = -2, ms = -1/2 (ii) n = 3, l = 2, ml = 1, ms = +1/2 (iii) n = 4, l = 1, ml = 0, ms = +1/2 (iv) n = 3, l = 2, ml = -2, ms = -1 (v) n = 3, l = 1, ml = -1, ms = +1/2 (vi) n = 4, l = 1, ml = 0, ms = +1/2

Bohr's model explained electrons can revolve only in certain permitted orbits whose angular could successfully explain stability of atoms and spectrum of unielectron species. Hydrogen spectrum consists of Lyman, Balmer, Paschen, Brackett and Pfund series. Bohr's theory could not explain spectrum of multi-electron species, Stark effect, Zeeman effect, dual nature of matter, de Broglie equation and Heisenberg uncertainty principle which lead to orbital concept. Electrons were filled in orbitals according to Aufbau's principle, Hund's Rule and Pauli's exclusion principle. Each electron is identified by four quantum numbers n, l, ml and ms out which n, l, ml was derived from Schrodinger's wave equation. Half-filled and completely filled orbitals are more stable due to exchange energy and symmetrical distribution of electrons.

Using Aufbau principle, write the ground state electronic configuration of following atoms. (i) Boron (Z = 5) (ii) Neon (Z = 10) (iii) Aluminium (Z = 13) (iv) Chlorine (Z = 17) (v) Calcium (Z = 20)