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Atomic structure key terms
Use these key terms for Atomic structure in AQA Chemistry 7405. The page is built from approved learning objectives for this topic and links back to the wider unit, topic hub, and related revision assets.
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key terms
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Topic
Atomic structure
Key terms
Atomic model
A conceptual representation of the structure of an atom, showing a central nucleus containing protons and neutrons surrounded by electrons in defined regions.
Isotope
An atom of a given element that has the same number of protons but a different number of neutrons, giving it a distinct mass number.
Proton
A subatomic particle found in the nucleus of an atom, with a relative charge of +1 and a relative mass of 1.
Electron
A subatomic particle that orbits the nucleus of an atom, with a relative charge of -1 and a negligible relative mass.
atom
The smallest unit of an element, consisting of a nucleus containing protons and neutrons, surrounded by electrons.
nucleus
The central part of an atom, made up of protons and neutrons, which contains most of the atom's mass.
atom
The smallest unit of an element, consisting of protons, neutrons, and electrons. In Fundamental particles, atom is used to explain use particle properties to compare atoms, ions and isotopes with A-Level Chemistry precision.
ion
An atom or molecule that has gained or lost one or more electrons, resulting in a net electrical charge.
Proton
A positively charged particle found in the nucleus of an atom, with a relative charge of +1 and a relative mass of 1.
Neutron
A neutral particle found in the nucleus of an atom, with a relative mass of 1 and no charge.
isotope
Atoms of the same element that have the same number of protons but different numbers of neutrons.
neutron number
The number of neutrons in an atom's nucleus, which contributes to the mass number of the isotope.
Ionisation
The process by which an atom or molecule gains or loses electrons to form a charged particle (ion).
Time‑of‑Flight Mass Spectrometer
A mass spectrometer that separates ions based on the time they take to travel a fixed distance after being accelerated, allowing determination of their mass‑to‑charge ratio.
mass spectrum
A graphical representation showing the relative abundance of ions detected by a mass spectrometer as a function of their mass-to-charge ratio.
isotopic abundance
The relative amount of each isotope of an element present in a sample, usually expressed as a percentage.
relative atomic mass
The weighted average mass of an atom of an element compared to 1/12th of the mass of a carbon-12 atom.
isotopic abundance
The relative amount of each isotope of an element present in a sample, usually expressed as a percentage.
isotope
Atoms of the same element that have the same number of protons but different numbers of neutrons.
mass spectrometry
A technique used to determine the relative abundance of isotopes and the relative atomic mass of elements.
Electron configuration
The arrangement of electrons in an atom’s shells and subshells, expressed using principal quantum numbers (n) and subshell labels (s, p, d, f).
Ionisation energy
The amount of energy required to remove an electron from a gaseous atom or ion, measured in kJ mol⁻¹.
first ionisation energy
The energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous ions.
ionisation energy trend
The general pattern observed in ionisation energies across periods and groups in the periodic table, typically increasing across a period and decreasing down a group.
first ionisation energy
The energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous ions.
successive ionisation energy
The energy required to remove one mole of electrons from one mole of gaseous ions after the first electron has been removed, resulting in a positively charged ion.
ionisation energy
The energy required to remove an electron from an atom or ion in its gaseous state.
electron configuration
The distribution of electrons among the energy levels and subshells of an atom.
ionisation energy
The energy required to remove one mole of electrons from one mole of gaseous atoms or ions.
Period 3 elements
Elements in the third row of the periodic table, including sodium, magnesium, aluminum, silicon, phosphorus, sulfur, chlorine, and argon.
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