What should I consider when building electron configurations?
Everything is based on energy. Nature always is most stable in the lowest energy configurations.
There are just a few rules/definitions to keep in mind in order to 'build up' atomic configurations properly. The first is the definition of the four quantum numbers (n, l ,
(a) The Principle Quantum number, n defines the energy of an electron in an atom and the size of an orbital.
(b) The Angular Momentum Quantum number, l defines the shape of an orbital.
(c) The Magnetic Quantum number,
(d) The Electron Spin Quantum Number
The four quantum numbers n, l ,
address, city, state, and postal code specify the address of an individual.
For example, the four quantum numbers for a 2s orbital electron are n = 2, l = 0,
There are four key principles or rules to keep in mind while constructing an atomic configuration.
- The Heisenberg Uncertainty Principle says that it is impossible to simultaneously know both the momentum and the position of an electron with certainty.
- The Aufbau Principle states that electrons fill subshells within an energy level from lowest level to highest.
- The Pauli Exclusion Principle says that “No two electrons in an atom can have the same four quantum numbers.”
- Hund's Rule states “the most stable arrangement of electrons in subshells is the one with the greatest number of parallel spins.” [electrons filling orbitals in a subshell with equal energy first spread out (parallel spins) before pairing up (opposite spins)].
With these basic rules you should be able to write out the electronic configuration of any atom or ion.