Phosphorus (P) has an atomic number of 15, which means it has 15 electrons in its neutral state. To achieve a noble gas electron configuration, phosphorus needs to gain three electrons.
A noble gas electron configuration refers to the electron configuration of a noble gas element, which has a completely filled outermost energy level (valence shell). Noble gases have stable electron configurations and are generally unreactive.
The electron configuration of phosphorus is 1s² 2s² 2p⁶ 3s² 3p³. To achieve a noble gas electron configuration, phosphorus can gain three electrons to fill its outermost energy level (3s² 3p⁶), similar to the noble gas neon (Ne).
By gaining three electrons, the electron configuration of phosphorus would become 1s² 2s² 2p⁶ 3s² 3p⁶, which matches the noble gas electron configuration of neon (Ne).