How Many Valence Electrons are in an Atom of Phosphorus?

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Detailed Solution

An atom of phosphorus has 5 valence electrons. Phosphorus has an atomic number of 15, and its electron configuration is 1s² 2s² 2p⁶ 3s² 3p³. The valence electrons are those in the outermost shell, which for phosphorus is the third shell. This shell contains 2 electrons in the 3s subshell and 3 electrons in the 3p subshell, totaling 5 valence electrons.

Write the Formula for Calcium Nitride:

The chemical formula for calcium nitride is written as Ca₃N₂.

Here is how to derive this formula:

Calcium (Ca) is a metal from group 2 of the periodic table and forms ions with a charge of +2 (Ca²⁺).
Nitrogen in the nitride ion form has a charge of -3 (N^3-).
To form a neutral compound, the total positive charge must balance the total negative charge.
The least common multiple of 2 and 3 is 6, so:
- You need 3 calcium ions (3 × +2 = +6).
- You need 2 nitride ions (2 × -3 = -6).
Combining these gives the formula Ca₃N₂.

This formula means 3 calcium ions bond with 2 nitride ions to make calcium nitride electrically neutral.

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