Question

model 1: # 2 why is mass number always a whole number? *
your answer
this is a required question
model 1: # 3 which isotope of carbon is used as the definition of the atomic * 1 point mass unit (amu)?
c - 15
c - 12
c - 11
c - 13
c - 14
c - 10

Explanation:

The mass number is calculated as the sum of protons and neutrons in an atom. Since the number of protons and neutrons must be whole numbers (you can't have a fraction of a proton or neutron), their sum (the mass number) is also always a whole number.

For the second question, by definition, the atomic mass unit (amu) is based on the carbon - 12 isotope. One atomic mass unit is defined as \(\frac{1}{12}\) of the mass of a carbon - 12 atom.

Answer:

For the first question: The mass number is the sum of protons and neutrons, both of which are whole numbers.
For the second question: B. C - 12