Q. Determine the Number of neutrons?

Isotopes of an element can as well be specified by writing the mass number of the isotope following a hyphen after the name of the element. For instance hydrogen's isotopes are able to be written as hydrogen-1 and hydrogen-2 or H-1 and H-2 respectively.

Evoke that the number of protons in an atom's nucleus is its atomic number. Alternative atomic number for the number of protons gives the following relationship.

Number of neutrons   =  mass number  +   atomic number

You are able to use this relationship to determine any one of the variables if you know the other two.