How many neutrons and protons does a typical neutral atom of phosphorus have?

1 Answer
Aug 10, 2016

The #""^31P# isotope is almost 100% abundant, #Z=15#, and thus there are 16 neutrons.

Explanation:

The atomic number, #Z#, of phosphorus is #15#. That is there are 15 #"protons"#, fundamental, positively charged, massive particles in the phosphorus nucleus. This atomic number defines the elemental identitiy. If there are 15 protons, then to make up the isotopic mass, #31#, there must be 16 #"neutrons"#, 16 massive, neutrally charged particles in the element's nucleus.