Definitions and concepts for AQA Chemistry A-level - Atomic Structure

1.1 Atomic Structure

Acceleration

Second stage of TOF spectrometry. The positively charged ions are accelerated by an electric field so that they have the same kinetic energy.

Atom

The smallest part of an element that can exist. All substances are made up of atoms.

Atomic nucleus

Positively charged object composed of protons and neutrons at the centre of every atom with one or more electrons orbiting it.

Atomic number

The number of protons in the nucleus.

Electron

Negatively charged subatomic particle which orbit the nucleus at various energy levels. Relative mass of 1/2000.

Electron configuration

The distribution of electrons of an atom in orbitals. E.g. Ca: 1s²2s²2p⁶3s²3p⁶4s².

Electron impact ionisation

Method of ionisation in TOF spectrometry. The sample is vaporised and an electron gun fires high energy electrons at it, causing an electron to be knocked off each particle to produce 1+ ions.

Electrospray ionisation

Method of ionisation in TOF spectrometry. The sample is dissolved and pushed through a fine nozzle at a high pressure. A high voltage is applied to it causing each particle to gain an H+ ion. The sample is then turned into a gas.