1s² 2s² 2p⁶ 3s² 3p³

Here's how to understand it:

* Phosphorus (P) has an atomic number of 15, meaning it has 15 protons and 15 electrons.

* Electron configuration describes the arrangement of electrons in an atom's energy levels and sublevels.

* 1s²: The first energy level (n=1) has one subshell, the 's' subshell, which can hold up to 2 electrons.

* 2s²: The second energy level (n=2) also has an 's' subshell, holding 2 electrons.

* 2p⁶: The second energy level has a 'p' subshell, which can hold up to 6 electrons.

* 3s²: The third energy level (n=3) has an 's' subshell, holding 2 electrons.

* 3p³: The third energy level also has a 'p' subshell, which contains 3 electrons in phosphorus.

Important Note: While this is the ground state electron configuration, you might also see phosphorus's configuration written as [Ne] 3s² 3p³. This shorthand notation uses the previous noble gas element (Neon, [Ne]) to represent the filled inner shells.