Advanced Higher Chemistry Vocabulary

Vocabulary flashcards covering key concepts in inorganic chemistry, physical chemistry, organic chemistry, instrumental analysis, and practical techniques.

Dual Nature of Electromagnetic Radiation

The concept that electromagnetic radiation can be described as a wave, possessing wavelength and frequency, and as a stream of particles called photons.

Photon

A particle of electromagnetic radiation carrying quantised energy that is directly proportional to the frequency of the radiation.

Principal Quantum Number ($n$)

A quantum number that indicates the main energy level for an electron and relates to the size of the atomic orbital.

Angular Momentum Quantum Number ($l$)

A quantum number that determines the shape of the subshell and can take integer values from $0$ to $n-1$.

Magnetic Quantum Number ($m_l$)

A quantum number that determines the spatial orientation of an orbital and can take integer values between $-l$ and $+l$.

Spin Magnetic Quantum Number ($m_s$)

A quantum number that determines the direction of electron spin and can have values of $+\frac{1}{2}$ or $-\frac{1}{2}$.

Aufbau Principle

A rule stating that electrons fill atomic orbitals in order of increasing orbital energy.

Hund's Rule

A rule stating that when degenerate orbitals are available, electrons fill each orbital singly with parallel spins before spin pairing occurs.

Pauli Exclusion Principle

A principle stating that no two electrons in an atom can have the same set of four quantum numbers, meaning an orbital can hold a maximum of two electrons with opposite spins.

Degenerate Orbitals

Atomic orbitals within the same subshell that possess equal energy in an isolated atom.

Transition Metals

D-block metals that have an incomplete d subshell in at least one of their oxidation state ions.

Ligands

Negative ions or neutral molecules containing non-bonding electron pairs that donate to a central transition metal atom or ion to form dative covalent bonds.

Coordination Number

The total number of dative covalent bonds formed from surrounding ligands to the central transition metal ion.

Spectrochemical Series

An order of ligands arranged according to their ability to cause d orbital splitting in transition metal complexes.

Heterogeneous Catalyst

A catalyst that exists in a different physical state from the reactants in a chemical reaction.

Homogeneous Catalyst

A catalyst that exists in the same physical state as the reactants in a chemical reaction.

Equilibrium Constant ($K$)

A dimensionless value that characterises the equilibrium composition of a reaction mixture at a constant temperature.

Ionic Product of Water ($K_w$)

The dissociation constant for the ionisation of water, expressed as $K_w = [\text{H}_3\text{O}^+][\text{OH}^-]$, equal to approximately $1 \times 10^{-14}$ at $25^\times\text{C}$.

Amphoteric

A chemical property describing a substance, such as water, that can act as both an acid and a base.

Brønsted-Lowry Acid

A substance that acts as a proton donor in a chemical reaction.

Brønsted-Lowry Base

A substance that acts as a proton acceptor in a chemical reaction.

Buffer Solution

A solution whose pH remains approximately constant when small amounts of acid, base, or water are added.

Standard Enthalpy of Formation ($Δ H_f^┆$)

The enthalpy change that occurs when one mole of a substance is formed from its constituent elements in their standard states.

Entropy ($S$)

A thermodynamic quantity that represents a measure of the degree of disorder in a system.

Second Law of Thermodynamics

A law stating that the total entropy of a reaction system and its surroundings always increases for a spontaneous process.

Third Law of Thermodynamics

A law stating that the entropy of a perfect crystal at $0\,\text{K}$ is zero.

Feasible Reaction

A reaction that tends towards the formation of products rather than reactants, occurring when the standard free energy change ($Δ G^┆$) is negative.

Rate Determining Step

The slowest elementary step in a multi-step reaction mechanism that governs the overall reaction rate.

Sigma ($σ$) Molecular Orbital

A molecular orbital formed by the end-on overlap of atomic orbitals along the axis of a covalent bond.

Pi ($π$) Molecular Orbital

A molecular orbital formed by the side-on overlap of parallel atomic orbitals perpendicular to the axis of a covalent bond.

Hybridisation

The process of mixing atomic orbitals within an atom to generate a set of new, degenerate hybrid orbitals.

HOMO

Highest Occupied Molecular Orbital, which is the highest energy molecular orbital that contains electrons.

LUMO

Lowest Unoccupied Molecular Orbital, which is the lowest energy molecular orbital that contains no electrons.

Chromophore

A specific group of atoms within an organic molecule responsible for absorbing light in the visible spectrum.

Conjugated System

A system of adjacent unhybridised p orbitals overlapping side-on to form a delocalised molecular orbital across multiple carbon atoms.

Homolytic Fission

Bond breaking where each atom retains one electron from the covalent bond, yielding two neutral radicals.

Heterolytic Fission

Bond breaking where one atom retains both electrons from the covalent bond, yielding two oppositely charged ions.

Nucleophile

An electron-rich neutral molecule or negatively charged ion capable of donating an electron pair to form a new covalent bond.

Electrophile

An electron-deficient neutral molecule or positively charged ion capable of accepting an electron pair to form a new covalent bond.

Markovnikov's Rule

A rule stating that when a hydrogen halide or water adds to an unsymmetrical alkene, the hydrogen atom attaches to the carbon with the higher number of hydrogen atoms.

Geometric Isomers

Stereoisomers that occur due to restricted rotation around a bond, designated as cis or trans based on substituent orientation.

Optical Isomers

Non-superimposable mirror-image stereoisomers (enantiomers) formed around a central chiral carbon atom bonded to four different groups.

Racemic Mixture

An optically inactive mixture containing equal amounts of two enantiomers, where opposing rotations of plane-polarised light cancel out.

Primary Standard

A stable, highly pure, soluble substance with a high GFM that can be weighed directly to prepare a standard solution.

Gravimetric Analysis

A quantitative analytical method used to measure the mass of an analyte by converting it into a substance of known chemical composition that can be isolated and weighed.

Acid Chloride Group

A functional group featuring a carbonyl carbon bonded to a chlorine atom, reacting rapidly with alcohols without a catalyst to produce esters.

Agonist

A drug molecule that mimics the natural active compound and binds to receptor molecules to trigger a biological response.

Antagonist

A drug molecule that binds to receptor molecules without activating them, blocking the natural active compound from producing a response.

Retention Factor ($R_f$)

The ratio of the distance travelled by a sample compound to the distance travelled by the solvent front in thin-layer chromatography.

Refluxing

A practical technique allowing heat energy to be supplied to a reaction mixture over an extended time period without loss of volatile reactants or products.