The only known atom that does not contain a neutron is one of the isotopes of hydrogen.The mass number,symbolized as "A" in the text,of this hydrogen isotope must be:
A)1.01
B)0
C)1
D)2
E)none of the above

Question

Quizplus · Accepted Answer

The mass number of an isotope is equal to the sum of its protons and neutrons. Since this hydrogen isotope does not contain a neutron, it must only have one proton. Therefore, its atomic number is 1, and the mass number is also 1. So, the best choice is C)1.

The Only Known Atom That Does Not Contain a Neutron