3.Zinc has an atomic number of 30 and a mass number of 65, how many neutrons does it have? 30
65
35
95

35

Explanation:

Given parameters:

  Atomic number of zinc  = 30

  Mass number of zinc = 65

Unknown

  Number of neutrons  = ?

Solution:

The mass number of an atom is the sum of its protons and neutrons;

     Mass number  = Protons + neutrons

Atomic number is the number of protons in an atom;

   Atomic number  = Protons

So;

     Mass number  = Atomic number + Neutrons

Neutrons  = Mass number  - Atomic number

 Neutrons  = 65 - 30  = 35

The number of neutrons in the atom is 35

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