What is the isotope symbol for an atom that contain 2 protons and 1 neutron?

To find the element, look at the number of protons. Because the number of protons defines what element is present, just look for the element with this . Taking a look at , we can see that the element with 2 protons is helium.

The overall mass of this element will be equal to the number of protons plus the number of neutrons. Because 2 + 1 = 3, that will be mass of this isotope.

As a result, this isotope can be represented by ##:^(3)He##

OK.