Atomic Number
An element’s atomic number is determined by how many protons are found in one of its atoms. Each atom in an element has precisely the same number of protons. For instance, the atomic number of carbon is “6” since all carbon atoms have six protons.
Regardless of the presence of neutrons, elements are classified according to the number of protons in their nuclei. Uncharged subatomic particles known as neutrons are stable when contained in an atomic nucleus. Except for hydrogen, all other elements’ atoms have neutrons in the nucleus. Hence,
Atomic Number = Number of Protons in an atom
Atomic Mass
Atomic mass is the total mass of all subatomic particles of an atom, including protons, neutrons, and electrons. However, the mass of electrons is incredibly small, so it’s typically neglected when determining an atom’s overall mass.
The unit commonly used to express atomic mass is the Atomic Mass Unit (AMU) and dalton, a non-SI unit. One dalton is equivalent to one-twelfth of the mass of a carbon-12 atom at rest in its ground state. This definition provides a standard reference point for measuring atomic masses.
The atomic mass of an individual atom is closely related to its mass number, which represents the total number of protons and neutrons in the nucleus. Since protons and neutrons contribute most to an atom’s mass, the atomic mass is nearly identical to the mass number. This relationship helps simplify calculations and understanding of atomic masses.