Question

What are the three rules for writing the electron configuration of elements

Answer 1

Answer:

The aufbau principle

The Pauli exclusion principle

Hund's rule of maximum multiplicity

Explanation:

The aufbau principle:

The fundamental electronic configuration is achieved by placing the electrons one by one in the different orbitals available for the atom, which are arranged in increasing order of energy.

The Pauli exclusion principle:

Two electrons of the same atom cannot have their four equal quantum numbers.  Because each orbital is defined by the quantum numbers n, l, and m, there are only two possibilities ms = -1/2 and ms = +1/2, which physically reflects that each orbital can contain a maximum of two electrons, having opposite spins

Hund's rule of maximum multiplicity:

This rule says that when there are several electrons occupying degenerate orbitals, of equal energy, they will do so in different orbitals and with parallel spins, whenever this is possible.  Because electrons repel each other, the minimum energy configuration is one that has electrons as far away as possible from each other, and that is why they are distributed separately before two electrons occupy  the same orbital.