1. Electron Configuration:
* The atomic number of phosphorus is 15, meaning it has 15 electrons.
* The electron configuration of phosphorus is 1s² 2s² 2p⁶ 3s² 3p³.
2. Third Energy Level:
* The third principal energy level (n=3) includes the 3s and 3p orbitals.
* The 3s orbital has 2 electrons (3s²).
* The 3p orbital has 3 electrons (3p³).
3. Total Electrons:
* Adding the electrons in the 3s and 3p orbitals: 2 + 3 = 5 electrons
Therefore, there are 5 electrons in the third principal energy level (n=3) of a phosphorus atom.
