Why is the atomic weight of hydrogen 1.008 and not exactly its mass number, 1.000?
a. Atomic weight does not take into account the weight of rare isotopes of an element.
b. Atomic weight is the average of the mass numbers of a representative sample of the element, including all its isotopes.
c. The atomic weight includes the weight of the electrons.
d. The atomic weight does not include the weight of the protons.
e. The mass number of an element is always lower than its atomic weight.
Answer: B