Topic C1 — Atomic Structure and the Periodic Table

Vocabulary flashcards covering atomic structure, subatomic particle properties, atomic and mass numbers, ions, elements, isotopes, and relative atomic mass.

Atomic radius

The radius of an atom, which measures about $0.1\,\text{nanometres}$ (or $1 \times 10^{-10}\,\text{m}$).

Nucleus

The middle part of the atom containing protons and neutrons; it has a positive charge, contains almost the whole mass of the atom, and has a radius of around $1 \times 10^{-14}\,\text{m}$ (around $\frac{1}{10\,000}$ of the atomic radius).

Proton

A heavy, positively charged subatomic particle located in the nucleus with a relative mass of $1$ and a relative charge of $+1$.

Neutron

A heavy, neutral subatomic particle located in the nucleus with a relative mass of $1$ and a relative charge of $0$.

Electron

A tiny, negatively charged subatomic particle that moves around the nucleus in electron shells, possessing a relative charge of $-1$ and a very small relative mass.

Nuclear symbol

A notation that indicates the chemical symbol of an element along with its mass number at the top and atomic number at the bottom.

Atomic number

The number of protons in the nucleus of an atom, which dictates the type of atom and equals the number of electrons in a neutral atom.

Mass number

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

Neutral atom

An atom that possesses no overall charge because it contains an equal number of protons and electrons, whose equal and opposite charges cancel out.

Ion

An atom or group of atoms that has lost or gained electrons, meaning the number of protons does not equal the number of electrons, giving it an overall charge.

Positive ion

An ion formed when an atom loses electrons, where the number of electrons is calculated as $\text{atomic number} - \text{charge}$.

Negative ion

An ion formed when an atom gains electrons, where the number of electrons is calculated as $\text{atomic number} + \text{charge}$.

Element

A substance made up entirely of atoms that all have the same number of protons in their nucleus.

Chemical symbol

A one- or two-letter abbreviation representing an element on the periodic table, such as $\text{C}$ for carbon, $\text{O}$ for oxygen, $\text{Na}$ for sodium, $\text{Mg}$ for magnesium, and $\text{Fe}$ for iron.

Isotopes

Atoms of the same element that have the same number of protons (same atomic number) but a different number of neutrons (different mass numbers).

Relative atomic mass ($A_r$)

An average mass of an element that accounts for the different masses and abundances of each of its isotopes.

Relative atomic mass formula

$$\text{Relative atomic mass } (A_r) = \frac{\text{sum of (isotope abundance} \times \text{isotope mass number)}}{\text{sum of abundances of all the isotopes}}$$