answersLogoWhite

0

Most helium has a mass number of 4. The rare 3He isotope has a mass number of 3.

The mass number is the integer total of protons and neutrons for a given isotope. For example radioactive carbon-14 has a mass number of 14, while carbon-12 (the most common stable form) has a mass number of 12.

User Avatar

Wiki User

13y ago

What else can I help you with?