Question

What is the mass number of an atom with 17 protons, 17 electrons, and 20 neutrons?

Answer 1

The mass number of this particular element is 37

An element with 17 protons will ALWAYS be chlorine.
The mass number is found by adding the element’s protons and neutrons.
protons+neutrons=mass number

Here is the math if needed,
17+20=37

Therefore the mass number is 37

I hope this helped!