What are the differences and similarities between atomic number and mass number?

Here are the differences and similarities between atomic number and mass number:

• Differences:

  • Atomic Number ($Z$): Represents the number of protons in an atom's nucleus. It uniquely identifies an element. For a neutral atom, it also equals the number of electrons.
  • Mass Number ($A$): Represents the total number of protons and neutrons in an atom's nucleus. It indicates the approximate mass of an atom. Different isotopes of the same element have the same atomic number but different mass numbers due to varying numbers of neutrons.

• Similarities:

  • Both are integer values.
  • Both relate to the composition of the atomic nucleus.
  • Both include the number of protons in their definition.