For a given atom, what is the mass number?

1 Answer
Mar 9, 2017

Answer:

The sum of protons and neutrons is the mass number.

Explanation:

And this sum gives the identity of the isotope.

For the simplest (and most abundant element), hydrogen, MOST hydrogen nuclei are garden variety #"protium"#, #""^1H#. A small proportion of hydrogen atoms are #"deuterium"#, #""^2H#. An even smaller proportion of hydrogen atoms are #"tritium"#, #""^3H#. What is the number of neutrons in each isotope?