Atomic Structure: Elements and Isotopes

Vocabulary flashcards reviewing fundamental terms related to atomic structure, isotopes, and relative atomic mass calculations.

Element

A substance made up of atoms that all contain the same number of protons in their nuclei.

Atomic Number (Z)

The number of protons in an atom’s nucleus; it defines which element the atom is.

Mass Number (A)

The total number of protons plus neutrons in an atom’s nucleus.

Isotope

Atoms of the same element that have the same atomic number but different numbers of neutrons, giving them different mass numbers.

Carbon-12

An isotope of carbon with 6 protons and 6 neutrons (mass number 12).

Carbon-13

An isotope of carbon with 6 protons and 7 neutrons (mass number 13).

Relative Atomic Mass (Ar)

The weighted average mass of the atoms of an element, taking into account the relative abundances of all naturally occurring isotopes, compared to one-twelfth of the mass of a carbon-12 atom.

Ar Calculation Formula

Ar = Σ(isotope abundance × isotope mass number) ÷ Σ(isotope abundances).

Copper Isotope Example (Cu-63 & Cu-65)

Using abundances of 69.2 % for Cu-63 and 30.8 % for Cu-65, the calculated relative atomic mass of copper is ≈ 63.6.