Electrons fill atomic orbitals in order of increasing energy.
This means that electrons will first occupy the lowest energy orbitals available before moving to higher energy orbitals. The order of filling is determined by the (n + l) rule, where:
* n is the principal quantum number (energy level)
* l is the azimuthal quantum number (subshell type, e.g., s, p, d, f)
Here's how it works:
1. Calculate (n + l) for each orbital. For example, for the 2p orbital, n = 2 and l = 1, so (n + l) = 3.
2. Order orbitals by increasing (n + l) value.
3. If two orbitals have the same (n + l) value, the orbital with the lower n value is filled first.
Example:
* 1s (n + l = 1)
* 2s (n + l = 2)
* 2p (n + l = 3)
* 3s (n + l = 3)
* 3p (n + l = 4)
* 4s (n + l = 4)
* 3d (n + l = 4)
* 4p (n + l = 5)
* 5s (n + l = 5)
* 4d (n + l = 5)
* 5p (n + l = 6)
* 6s (n + l = 6)
* 4f (n + l = 6)
Important notes:
* The Aufbau principle is a helpful guideline for predicting electron configurations, but it's not always perfect. There are some exceptions due to factors like electron-electron repulsion and the stability of half-filled and fully filled subshells.
* The Aufbau principle is mainly used for understanding the electronic structure of atoms in their ground state (lowest energy state).
By following the Aufbau principle, we can understand how electrons are distributed within an atom's orbitals and how this distribution determines the atom's chemical properties.
