AQA Atomic Structure Flashcards

A comprehensive set of vocabulary flashcards covering the AQA atomic structure specification, including atomic history, mass spectrometry, electron configurations, and ionization energy trends.

Proton

A subatomic particle located in the nucleus with a positive charge and a relative mass of $1$.

Neutron

A subatomic particle located in the nucleus with a zero (neutral) charge and a relative mass of $1$.

Electron

A negatively charged subatomic particle that orbits the nucleus in shells, with a relative mass of $\frac{1}{2000}$.

Mass number

The top number on an element in the periodic table, representing the total number of protons and neutrons in the nucleus.

Atomic number

Also known as the proton number, it is the bottom number indicating the number of protons in an atom.

Ions

Atoms that have gained or lost electrons, resulting in a different number of electrons than protons and thus an overall charge.

Isotopes

Atoms of the same element with the same number of protons but a different number of neutrons, resulting in a different mass but identical chemical reactions.

John Dalton (1803)

A scientist who proposed the early atomic theory that atoms were very simple, solid spheres.

JJ Thompson

The scientist who discovered the electron and proposed the Plum Pudding model, where an atom is a positive 'pudding' containing negative electrons.

Ernest Rutherford

The scientist who discovered the small positive nucleus using the Gold Leaf experiment and proposed that most of the atom is empty space.

Niels Bohr (1913)

A scientist who proposed the shell model, suggesting that electrons exist in fixed energy levels to prevent the electron cloud from collapsing into the nucleus.

Electrospray ionization

A technique in mass spectrometry where a sample is sprayed through a high-pressure jet under high voltage, causing the loss of an electron to form gaseous $1+$ ions.

m/z ratio

The mass-to-charge ratio used in mass spectrometry; if the charge is $+1$, this value is equivalent to the mass of the isotope.

Relative atomic mass ($A_r$)

The average mass of an atom of an element measured on a scale where the mass of an atom of carbon 12 is exactly $12$.

Relative molecular mass ($M_r$)

The average mass of a molecule measured on a scale where the mass of an atom of carbon 12 is exactly $12$.

Relative isotopic mass

The mass of an atom of an isotope of an element measured on a scale where the mass of an atom of carbon 12 is exactly $12$.

Molecular ion peak (M+1)

The last significant peak on a mass spectrum, representing the unfragmented molecule that has been ionized.

Orbitals

Regions within subshells (s, p, d, f) that can each hold a maximum of two electrons spinning in opposite directions.

Transition metal ionization rule

The principle that transition metals lose electrons from the $4s$ subshell before the $3d$ subshell when forming ions.

Chromium and Copper exceptions

Transitions metals that behave differently because an electron moves from the $4s$ orbital to the $3d$ orbital to create more stable half-full or full subshells.

First ionization energy

The minimum amount of energy required to remove one mole of electrons from one mole of atoms in the gaseous state.

Shielding

The reduction in attractive force between the positive nucleus and outer electrons due to the presence of internal electron shells.

Successive ionization

The removal of multiple electrons from the same atom, where large jumps in energy provide evidence for different electron shells.

Group trend in ionization energy

The first ionization energy decreases down a group due to increased atomic radius and shielding, which weakens the attraction to the outer electron.

Period trend in ionization energy

The first ionization energy generally increases across a period due to increased nuclear charge while shielding remains similar.

Aluminium ionization anomaly

A decrease in ionization energy compared to magnesium because the outer electron sits in a higher energy $3p$ subshell further from the nucleus and is shielded by the $3s$ orbital.

Sulfur ionization anomaly

A decrease in ionization energy compared to phosphorus caused by electron repulsion in a paired $3p$ orbital, making the electron easier to remove.