Question #8d740

1 Answer
MeneerNask
Dec 18, 2016

It is the difference between mass number #Z# and the atomic number #A#. In a neutral atom the number of electrons is the same as the number of protons.

Explanation:

Example: Chlorine-35 has a mass number of #Z=35#
From the periodic table we see that the atomic number #A=17#, which is also the number of protons.

Now the number of neutrons #=Z-A=35-17=18#

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