Atom: The smallest particle of an element that can exist and still retain the chemical properties of that element.
Element: A substance made of only one type of atom, which cannot be broken down into simpler substances by chemical means.
Atomic number (Z): The number of protons in the nucleus of an atom. This is unique to each element.
Mass number (A): The total number of protons and neutrons (nucleons) in the nucleus of an atom.
Isotope: Atoms of the same element with the same number of protons but different numbers of neutrons, giving different mass numbers.
Relative atomic mass (Ar): The weighted mean mass of an atom of an element compared to one-twelfth of the mass of a carbon-12 atom.
This definitions covers Key Definitions within Atomic Structure for GCSE Chemistry. Revise Atomic Structure in Atomic Structure for GCSE Chemistry with 28 exam-style questions and 22 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 9 of 14 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.
Practice questions for Atomic Structure
What does the atomic number of an element tell you?
Explain what is meant by the relative atomic mass of an element and how it is calculated from isotopic data. [3 marks]