If an atom of tin has a mass number of 118 and an atomic number of 50, how many neutrons are in its nucleus?

1 Answer
anor277
Oct 28, 2016

There must be 68 neutrons in a ""^118Sn118Sn isotope.

Explanation:

The mass number relates to the massive particles: protons, and neutrons. Since there are 50 protons, there MUST be 68 neutrons.

Note that an examiner would be quite justified in asking you this question WITHOUT advice as to ZZ, the atomic number, if tin metal were specified. Do you agree?

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