Question

Distinguish between mass number and atomic mass.

a) Mass number represents the total number of protons and neutrons in an atom.
b) Atomic mass is the mass of an atom relative to the mass of a carbon-12 atom.
c) Mass number is the sum of protons and electrons in an atom.
d) Atomic mass is the total number of protons in an atom.

Answer 1

The mass number is the sum of protons and neutrons in an atom's nucleus, while the atomic mass is a decimal representing the average mass of an element's isotopes relative to carbon-12.

Step-by-step explanation:

The mass number and the atomic mass are two different quantities that help characterize an atom. The mass number (A) is defined as the total number of protons and neutrons in the nucleus of an atom, which gives a whole number. It helps to differentiate one atom from another, particularly isotopes of the same element which have the same atomic number but a different mass number.

The atomic mass, on the other hand, is a weighted average of all of the isotopes of an element measured in atomic mass units (amu) relative to the mass of a carbon-12 atom. This is a decimal value because most elements exist as mixtures of isotopes.