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 #""^118Sn# 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 #Z#, the atomic number, if tin metal were specified. Do you agree?

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