The atomicity of phosphorus is 4. This means that a single atom of phosphorus has 4 valence electrons. Valence electrons are the electrons in the outermost shell of an atom that are involved in chemical bonding. The number of valence electrons determines the chemical properties of an element. Phosphorus is a non-metal that is found in Group 15 of the periodic table. It is a highly reactive element that is used in a variety of industrial applications, including fertilizers, pesticides, and semiconductors.
Option A: 3 is incorrect because phosphorus does not have 3 valence electrons.
Option B: 4 is correct because phosphorus has 4 valence electrons.
Option C: 5 is incorrect because phosphorus does not have 5 valence electrons.
Option D: 7 is incorrect because phosphorus does not have 7 valence electrons.