Structure of the Atom

Vocabulary flashcards covering the structure of the atom, subatomic particles, historical models, and atomic notation.

Atom

The smallest particle of an element that still has the properties of that element, derived from a Greek word meaning 'cannot be cut'.

Subatomic particle

A tiny particle found inside an atom, such as a proton, neutron, or electron.

Proton

A positively charged subatomic particle situated in the nucleus with a relative mass of $1\text{ unit}$ and a relative charge of $+1$.

Neutron

A neutral subatomic particle situated in the nucleus with no charge ($0$) and a relative mass of $1\text{ unit}$.

Electron

A negatively charged subatomic particle situated outside the nucleus in the electron cloud with a relative mass of $\frac{1}{1,840}\text{ unit}$ and a relative charge of $-1$.

Nucleus

The very small, central part of an atom that contains the protons and neutrons.

Electron cloud

The region outside the nucleus of an atom in which electrons revolve in orbits.

Orbits (shells)

The fixed paths around the centre or nucleus of an atom in which electrons move.

Planetary model

Niels Bohr's model of the atom proposing that electrons revolve around the nucleus just like planets move around the sun.

John Dalton

The English scientist who put forward an atomic theory in 1808 proposing that all elements are composed of tiny indivisible particles called atoms.

Niels Bohr

The Danish scientist who proposed in 1913 that electrons move around the nucleus in fixed paths called orbits, winning the Nobel Prize for Physics in 1922.

Atomic number

The number of protons in the nucleus of an atom.

Mass number

The total sum of the numbers of protons and neutrons in the nucleus of an atom.

Atomic mass unit (amu)

The special unit used to measure the mass of atoms instead of grams.

Nuclear formula

A shorthand method of writing an element's symbol displaying its mass number at the top and atomic number at the bottom (e.g., $^{27}_{13}\text{Al}$).

Calculation of neutrons

The formula used to determine neutrons in an atom: $\text{number of neutrons} = \text{mass number} - \text{atomic number}$.