The electron configuration of an atom is the particular distribution of electrons among available shells. It is described by a notation that lists the subshell symbols, one after another. Each symbol has a superscript on the right giving the number of electrons in that subshell. For example, a configuration of the lithium atom (atomic number 3) with two electrons in the 1s subshell and one electron in the 2s subshell is written 1s22s1. The notation for electron configuration gives the number of electrons in each subshell. Few exceptional are electronic configuration of copper.
The atom is built up by filling electrons in various orbitals according to the following rules. For More Chemistry Formulas check out Main page of Physics Wallah.
Aufbau Principle: This principle states that the electrons are added one by one to the various orbitals in order of their increasing energy starting with the orbital of lowest energy. The increasing order of energy of various orbital is
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