A-Level Chemistry OCR B Year 1

Atom

The basic unit of a chemical element, composed of a nucleus surrounded by electrons.

Nucleus

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

Proton

A subatomic particle found in the nucleus of an atom, with a relative charge of +1 and a relative mass of 1.

Neutron

A subatomic particle found in the nucleus of an atom, with no charge (neutral) 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 very small mass (1/2000 of a proton).

Mass Number

The total number of protons and neutrons in an atom's nucleus.

Atomic Number

The number of protons in the nucleus of an atom, also known as the proton number.

Plum Pudding Model

An early model of atomic structure proposed by J.J. Thompson, which described atoms as having a positive charge with electrons distributed throughout.

Gold Leaf Experiment

A famous experiment conducted by Ernest Rutherford that demonstrated the presence of a small, dense positively charged nucleus in an atom.

Electron Shells

Regions around the nucleus where electrons are likely to be found, described by their energy levels.

Quantum Model

The modern description of atomic structure that includes the concept of electron subshells and orbitals.

Nuclear Fusion

A reaction where two nuclei combine to form a heavier nucleus, often occurring in the sun.

Subshells

Different energy levels within electron shells that include s, p, d, and f orbitals.

Spin Pairing

The concept that two electrons in the same orbital must have opposite spins.

Electron Configuration

The arrangement of electrons in an atom, denoted by shell numbers, subshell types, and the number of electrons in each subshell.

Transition Metals

Elements found in the d block of the periodic table that behave differently in terms of their electron configurations.

S Block Elements

Elements in which the outermost electrons are in the s orbital, typically groups 1 and 2 in the periodic table.

P Block Elements

Elements in which the outermost electrons are in the p orbital, typically groups 13 to 18 in the periodic table.

F Block Elements

Elements where the outermost electrons are in the f orbital, typically found at the bottom of the periodic table.

Ionic Bonding

The electrostatic attraction between oppositely charged ions.

Electrostatic Attraction

The force that attracts positively and negatively charged ions to each other.

Octet Rule

Atoms tend to gain, lose, or share electrons to have eight electrons in their outer shell.

Molecular Ions

Charged ions made up of two or more atoms, such as hydroxide (OH-) and sulfate (SO4^2-).

Swap and Drop Method

A technique used to determine the formula of an ionic compound by swapping the charges of the ions.

Giant Ionic Structure

A regular arrangement of ions in a repeating three-dimensional pattern.

Melting Point

The temperature at which a solid becomes liquid, influenced by the strength of ionic bonds in an ionic compound.

Covalent Bonding

A type of bonding where atoms share electrons to achieve a full outer shell.

Dative Covalent Bond

A bond formed when one atom provides both electrons for a pair in a bond.

Giant Covalent Structures

Structures, such as graphite and diamond, where atoms are bonded in extensive networks.

Delocalized Electrons

Electrons that are free to move in a 'sea' around positively charged metal ions in metallic bonding.

Metallic Bonding

The attraction between positively charged metal ions and delocalized electrons.

Polarity

A property of molecules where there is an uneven distribution of electron density.

Tetrahedral Shape

A molecular shape with four bond pairs and no lone pairs, with bond angles of 109.5 degrees.

Bond Angles

The angles between adjacent bonds in a molecule, influenced by lone pairs.

Linear Shape

A molecular shape resulting from two bond pairs and no lone pairs, with bond angles of 180 degrees.

Trigonal Planar Shape

A molecular shape resulting from three bond pairs and no lone pairs, with bond angles of 120 degrees.

Square Planar Shape

A molecular configuration for four bond pairs and two lone pairs, with bond angles of 90 degrees.

Electromagnetic Spectrum

The range of all types of electromagnetic radiation, arranged by frequency and wavelength.

Emission Spectrum

A spectrum of the electromagnetic radiation emitted by a source, showing specific wavelengths corresponding to the energy transitions of electrons.

Absorption Spectrum

A spectrum that shows dark lines or bands on a continuous spectrum, indicating specific wavelengths of radiation absorbed by electrons.

Quantum Level

Discreet energy levels in an atom where electrons reside, with defined energy values and no in-between states.

Ground State

The lowest energy state of an electron in an atom, closest to the nucleus.

Planck's Constant (h)

A fundamental constant used in quantum mechanics, representing the proportionality between the energy of a photon and its frequency.

Flame Test

A qualitative analysis technique used to identify the presence of certain metal ions based on the color of flame produced.

Mass Spectrometer

An analytical device that measures the mass-to-charge ratio of ions to identify and quantify substances.

Isotope

Atoms of the same element that have the same number of protons but different numbers of neutrons, resulting in different masses.

Mass number

The sum of protons and neutrons in an atom's nucleus.

Atomic number

The number of protons in the nucleus of an atom, which also equals the number of electrons in a neutral atom.

Ion

An atom or molecule that has gained or lost one or more electrons, resulting in a positive or negative charge.

Isotope

Atoms of the same element that have the same number of protons but different numbers of neutrons.

Relative atomic mass (AR)

The weighted average mass of an atom of an element compared to 1/12th of the mass of a carbon-12 atom.

Mole

A unit of measurement for the amount of substance, defined as containing 6.02 x 10²³ particles, known as Avogadro's number.

Avogadro's number

6.02 x 10²³, the number of particles in one mole of a substance.

Concentration

The amount of a substance in a given volume; expressed in moles per decimeter cubed (mol/dm³).

Empirical formula

The simplest whole number ratio of atoms of each element in a compound.

Molecular formula

A formula that shows the actual number of atoms of each element in a molecule of a compound.

Water of crystallization

Water molecules that are chemically bound to a hydrated compound, affecting its mass.

Percentage yield

A measure of the efficiency of a reaction, calculated as actual yield divided by theoretical yield times 100.

Titration

A laboratory method to determine the concentration of a solution by reacting it with a solution of known concentration.

Proton Number

The number of protons in the nucleus of an atom, which determines the atomic number and position in the periodic table.

Group

A column in the periodic table where elements have similar chemical properties and the same number of electrons in their outer shell.

Ionization Energy

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

S-Block Elements

Elements in the periodic table whose outermost electrons are in the s orbital, including groups 1 and 2.

P-Block Elements

Elements in the periodic table whose outermost electrons are in the p orbital, including groups 13 to 18.

Melting Point Trend Across Period 3

Melting points generally increase from sodium to aluminum due to stronger metallic bonding and increasing ionic charge.

Covalent Bonding

A type of chemical bond involving the sharing of electron pairs between atoms.

Thermal Decomposition

A chemical reaction where a compound breaks down into simpler compounds or elements upon heating.

Solubility

The ability of a substance to dissolve in a solvent, affecting how ions interact in solutions.

Hydroxide Ion (OH-)

A negatively charged ion formed when an alkali dissolves in water, responsible for the basic properties of solutions.

Precipitation Reaction

A chemical reaction that occurs in an aqueous solution, resulting in the formation of an insoluble solid.

Flame Test

A qualitative analysis technique used to detect the presence of certain metal ions based on the color of the flame produced.

Chelation

The formation of complex structures by ions with surrounding molecules or anions that stabilize them.

D-Block Elements

Transition metals located in the center of the periodic table, known for variable oxidation states.

Alkaline Solutions

Solutions that contain hydroxide ions and have a pH greater than 7, capable of neutralizing acids.

Ammonium Ion (NH4+)

A positively charged polyatomic ion formed when ammonia dissolves in water.

Colored Precipitate for Cations

The formation of solid colors when certain metal ions react with different reagents, indicating their presence.

Group Two Reactivity Trend

Reactivity of group two metals increases as you move down the group due to larger atomic radius and decreased ionization energy.

Titration

A laboratory method used to determine the concentration of a solution by adding a solution of known concentration until a reaction is completed.

Acid-Base Neutralization

The process where an acid reacts with a base to produce salt and water.

Barium Sulfate

An insoluble white precipitate formed when mixing barium chloride with sulfate ions.

Alkane

A saturated hydrocarbon with the general formula CnH2n+2.

Cycloalkane

A saturated hydrocarbon in a ring structure with the general formula CnH2n.

Alkene

An unsaturated hydrocarbon with the general formula CnH2n, containing one double bond.

Aromatics (Arenes)

Organic compounds containing a benzene ring structure.

IUPAC

International Union of Pure and Applied Chemistry, the global standard for naming chemical compounds.

Homologous Series

A group of compounds with the same functional group and similar chemical properties, differing by CH2 units.

Chain Isomerism

Isomers with the same molecular formula but different arrangements of the carbon skeleton.

Positional Isomerism

Isomers with the same molecular formula but different positions of functional groups.

Functional Group Isomerism

Isomers with the same molecular formula but different functional groups.

Skeletal Formula

A representation of a molecule that shows only the bonds and the arrangement of the carbon skeleton.

General Formula

An algebraic formula that represents a family of compounds.

Sigma Bond

A type of covalent bond formed by the direct overlap of orbitals, creating a strong bond.

Pi Bond

A type of covalent bond formed by the parallel overlap of p-orbitals, typically weaker than sigma bonds.

Functional Group

A specific group of atoms within a molecule that is responsible for characteristic chemical reactions.

Tetrahedral Shape

The molecular shape of alkanes, with bond angles of 109.5 degrees.

Trigonal Planar

The molecular shape around a double bond with bond angles of 120 degrees.

Molecular Formula

A formula indicating the exact number of each type of atom in a molecule.

Alcohol

An organic compound containing one or more hydroxyl (-OH) functional groups.

Mole

A unit of measurement for amount of substance, defined as containing exactly 6.022 x 10²³ particles.

Molar gas volume

The volume occupied by one mole of a gas, typically 24 dm³ at 298 K and 101.3 kPa.