What is the mass number of a chlorine atom that has 19 neutrons? 

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The atomic number of chlorine is 17. An atom of chlorine has 17 protons. The mass of chlorine is the sum of all the elementary particles present in the atom which includes protons, neutrons and electrons. The mass of electrons, being very small is usually ignored. And the mass of...

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The atomic number of chlorine is 17. An atom of chlorine has 17 protons. The mass of chlorine is the sum of all the elementary particles present in the atom which includes protons, neutrons and electrons. The mass of electrons, being very small is usually ignored. And the mass of protons and neutrons is considered to be equal.

As the atom of chlorine has 19 neutrons, the mass number of chlorine is 17 + 19 = 36 

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