Rules to filling electrons in the orbitals and Shells
The electron configuration is the distribution of electrons of an atom or molecule in atomic or molecular orbitals. The number of electrons in an atom is the atomin number(Z) or the amount of protons of the atom. The number of electrons in an ion of an atom equals to the atomin number (Z) minus the ion charge.
When an atom or ion receives electrons into its orbitals, the orbitals and shells fill up in a particular manner based on following rules:
Aufbau principle:
- Electrons fill the lowest available energy level first i.e. electrons fill in electrons by order of energy, from low to high.
Pauli Exclusion principle:
- An orbital can hold a maximum of 2 electrons. These electons must have oppsite spins.
There are four different orbitals : s, p, d, and f
- There is one s orbital. Hence s orbital holds 2 electrons.
- There are three p orbitals. Hence p orbital holds 6 electrons.
- There are five d orbitals. Hence d orbital holds 10 electrons.
- There are seven f orbitals. Hence f orbital holds 14 electrons.
Hunds rule:
- Electrons will occupy an open orbital before it will pair up.