Question #8d740

1 Answer
MeneerNask
Dec 18, 2016

It is the difference between mass number ZZ and the atomic number AA. 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=35Z=35
From the periodic table we see that the atomic number A=17A=17, which is also the number of protons.

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

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