Chemistry > Structure of Atom > 14.0 Electronic Configuration of Elements
Structure of Atom
1.0 Introduction
2.0 Cathode Ray Discharge Tube
3.0 Thomson Model of Atom
4.0 Rutherford Model of Atom
5.0 Atomic Number and Mass Number and It's Relation
6.0 Planck's Quantum Theory
7.0 Bohr’s Atomic Model
8.0 Dual Behaviour of Matter
9.0 Heisenberg Uncertainity Principle
10.0 Photoelectric Effect
11.0 Atomic Spectra
12.0 Quantum Mechanical Model of Atom
13.0 Quantum Number
14.0 Electronic Configuration of Elements
14.1 Aufbau (or building up) Principle
14.2 Pauli’s Exclusion Principle
14.3 Hund’s Rule
14.4 Stability of Completely Filled and Half Filled Subshells
14.1 Aufbau (or building up) Principle
14.2 Pauli’s Exclusion Principle
14.3 Hund’s Rule
14.4 Stability of Completely Filled and Half Filled Subshells
- This principle is concerned with the energy of the atom.
- The electrons occupy the orbitals in such a way that the energy of atom is minimum. In other words the electrons in an atom are filled in the increasing order of their energies.
- We need to consider both n and l. This means that different sub-shells in a given shell have different energies. The order of orbital energies can be determined by the following (n + l) rules.
Rule 1: An orbital with a lower value for (n + l) has lower energy. For example, the 4s orbital (n + l = 4+0=4) will fill before a 3d orbital (n + l = 3 + 2 =5).
Rule 2: If the value of (n + l) is same for two orbitals then the orbital with lower value of n will be filled first. For example, the 3d orbital (n + l = 3+2=5) will fill before a 4p orbital (n + l = 4 + 1 =5).
Following these rules the increasing order of the orbital energies comes out to be
1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s
