Structure 3: Classification of matter

Group of periodic table

A column in the periodic table. There are 18 groups in the periodic table, numbered 1 to 18.

Period of periodic table

A horizontal row in the periodic table; the period number tells you how many electron shells an element has.

Metal

An element on the left-hand side of the periodic table that exhibits physical properties of malleability, lustre, high melting point, high electrical and thermal conductivity.

Non-metal

An element on the right-hand side of the periodic table that typically exhibits physical properties of being brittle, dull, lower melting point, low electrical and thermal conductivity.

Metalloid

An element that is located between metals and non-metals in the periodic table and shows intermediate properties between a metal and a non−metal.

Alkali metals

Elements in group 1; Soft metals that are very reactive with water and many non-metals.

Alkaline earth metals

Elements in group 2.

Lanthanides

Elements in 4p block.

Actinides

Elements in 5p block.

Transition elements

All elements in d-block; Transition elements can form ions with different ionic charges.

Triels

Elements in group 13.

Tetrels

Elements in group 14.

Pnictogens

Elements in group 15.

Chalcogens

Elements in group 16.

Halogens

Elements in group 17; Highly reactive and form ionic salts when they react with metals.

Noble gases

Elements in group 18; Colourless monatomic gases that have little to no reactivity with other elements.

Atomic radius

The distance from an atom's nucleus to the outermost orbital of one of its electrons.

Effective nuclear charge

The net positive charge from the nucleus experienced by outer valence shell electrons once the screening effect of the core electrons has been considered.

Periodicity

A repeating pattern or general trend of changing properties that is linked to atomic structure.

Periodicity of atomic radius

Increases as you go down a group due to additional energy levels/electron shells and decreases as you move across a period due to increase in effective nuclear charge.

Isoelectronic

Molecules with the same electron configuration.

Periodicity of Ionic radius for positive ions

Smaller in size than their parent atoms due to loss of electrons in the outermost shell increasing attraction between nucleus and the valence shell electrons.

Periodicity of Ionic radius for negative ions

Larger in size than their parent atoms due to increased repulsion between electrons in the valence shell decreasing the overall attraction between nucleus and valence shell electrons.

Ionisation energy

The energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions.

First ionisation energy

The energy required to remove one mole of the most loosely held electrons from one mole of gaseous atoms in the ground state.

Periodicity of Ionisation energy going down a group

Decreases since atomic radius increases and electrons occupy higher energy levels.

Periodicity of Ionisation energy moving across a period

Increases since nuclear charge increases (more protons in the nucleus) and atomic radius decreases which requires more energy to remove an electron.

Electron affinity

The amount of energy released when a neutral atom gains an electron to form a negatively charged ion.

First electron affinity

The release of energy that occurs when a neutral, gaseous atom gains one electron.

Periodicity of Electron Affinity

The absolute value for first electron affinity generally decreases going down a group since elements further down have a larger atomic radius, with outer valence shells further away from the nucleus causing weaker attraction between the added electron and the nucleus.

Electron Affinity Across a Period

Absolute value for first electron affinity generally increases going across a period since elements across the period have a higher effective nuclear charge causing stronger attraction between the added electron and the nucleus.

Electronegativity

A measure of how much an atomic nucleus attracts the shared electrons that are involved in a covalent bond.

Electronegativity Down a Group

Electronegativity values generally decrease down a group. Atomic radius increases down a group from additional energy levels, leading to weaker attraction between the nucleus and the shared pair of electrons.

Electronegativity Across a Period

Electronegativity values generally increase going across a period due to increasing effective nuclear charge, resulting in stronger attraction between the nucleus and the shared pair of electrons.

Metallic Character

The tendency of an element to lose electrons to form positive ions.

Non-metallic Character

The tendency of an element to gain electrons to form negative ions.

Metallic Character Periodicity

Increases across a period, decreases down the group.

Non-metallic Character Periodicity

Decreases across a period, increases down the group.

Reactivity of Group 1 Metals with Water

Increasing reactivity going down group 1 since elements have lower first ionisation energies due to the presence of an additional energy level.

Displacement Reaction

A reaction where a less reactive element is removed from a compound by a more reactive element.

Spectator Ion

Aqueous ions that remain unchanged throughout a chemical reaction.

Reactivity of Group 17 Halogens

Decreasing reactivity going down the group since the absolute value of electron affinity decreases.

Amphoteric

A substance that behaves both as an acid or a base.

Ocean Acidification

Ocean acidification decreases the pH of seawater, reducing the availability of carbonate ions needed by marine organisms like corals and shellfish to build their calcium carbonate shells and skeletons.

Acid Rain

Precipitation that has become acidic as it contains high levels of sulfuric acid or nitric acid due to air pollution.

Oxidation State

A number assigned to an element showing the number of electrons lost or gained (or even shared) in a compound or ion.

Oxyanions

Negatively charged polyatomic ions composed of oxygen bonded to another element.

Catenation

The ability of carbon to form bonds with other carbon atoms to produce chains and ring structures.

Full Structural Formula

A type of formula used to represent an organic compound in a lewis diagram format.

Condensed Structural Formula

A type of formula used to represent organic compounds that omits the bonds between the atoms.

Skeletal Formula

A type of formula that only shows the carbon skeleton (or backbone) of an organic compound, where each vertex represents a carbon.

Stereochemical Formula

A type of formula used to represent the 3D structure of an organic compound.

Ball and Stick Model

A type of molecular model used to represent an organic compound in which the atoms are depicted as balls and the bonds between them as sticks.

Alkanes

A class of organic compounds with single carbon to carbon bonds.

Alkenes

A class of organic compounds with double carbon to carbon bonds.

Alkynes

A class of organic compounds with triple carbon to carbon bonds.

Alkynes

A class of organic compounds triple carbon to carbon bonds.

Hydrocarbons

A compound containing the elements carbon and hydrogen only.

Saturated

An organic compound that contains C-C bonds only.

Unsaturated

An organic compound that contains C=C bonds or C≡C bonds.

Alkyl group

A branch of an organic compound that contains a saturated alkane in which one hydrogen has been removed to allow the branch to covalently bond to the parent chain.

Alcohols

A class of organic compounds that contain a hydroxyl functional group.

Hydroxyl functional group

Composed of an oxygen atom bonded to a hydrogen atom (R-OH), found in alcohols.

Aldehydes

A class of organic compounds that contain a terminal carbonyl functional group (at the end of the chain).

Carbonyl functional group

Composed of a carbon atom with a double bond to an oxygen atom (C=O).

Ketones

A class of organic compounds that contain a carbonyl functional group in the middle of the chain.

Carboxylic acids

A class of organic compounds that contain a carboxyl functional group.

Carboxyl functional group

Composed of a carbon atom bonded to a carbonyl group and a hydroxyl group (R-COOH).

Esters

A class of organic compounds that contain an ester functional group.

Ester functional group

Composed of a carbonyl group with a single bond to an oxygen atom (RCOOR').

Ethers

A class of organic compounds that contain an alkoxy functional group.

Alkoxy functional group

Composed of an oxygen atom bonded to two alkyl groups (R-O-R).

Amines

A class of organic compounds that contain an amino functional group.

Amino functional group

Composed of a nitrogen atom bonded to hydrogen atoms or alkyl groups (R-NH2).

Halogenoalkanes

A class of organic compounds that contain a halogeno functional group.

Halogeno functional group

Composed of a halogen atom bonded to an alkane (R-X).

Arenes

A class of organic compounds that contain a phenyl functional group.

Aromatic hydrocarbons

Hydrocarbon compounds that contain a benzene ring structure.

Phenyl functional group

Composed of six carbon atoms and five hydrogen atoms in a ring structure (C6H5-R).

Non-polar organic compounds

Compounds such as the alkanes, alkenes and alkynes will only have London dispersion forces acting between their molecules and tend to have lower boiling points, in other words they are more volatile.

Polar organic compounds

Compounds such as aldehydes and ketones have not only London dispersion forces acting between their molecules but also dipole-dipole attractions.

Compounds with N-H or O-H bonds

Alcohols, carboxylic acids and amides, have hydrogen bonds acting between their molecules.

Stem name

Indicates the number of carbon atoms in the parent chain.

Parent chain

The longest continuous chain of carbon atoms in an organic compound.

Suffix

Comes after the stem name and differs according to the functional group present in the molecule.

Prefix

Comes before the stem name and indicates the position of any substituent groups.

Substituent groups

An atom or group of atoms that replaces a hydrogen atom bonded to the parent chain of an organic compound.

Straight-chain alkanes

Alkanes in which the carbon atoms are arranged in a continuous chain with no branches.

Diols

An alcohol that contains two hydroxyl functional groups.

Triols

An alcohol that contains three hydroxyl functional groups.

Structural isomers

Compounds with the same molecular formula but different structural arrangements.

Mono-unsaturated compounds

Compounds that contain one C=C bond.

Position isomers

Same molecular formula but differ in the position of the functional group.

Functional group isomers

Same molecular formula but different functional groups.

Chain isomers

Same molecular formula but parent chain has a different length.

Primary carbon atom

Bonded to only one other carbon atom.

Secondary carbon atom

Bonded to two other carbon atoms.

Tertiary carbon atom

Bonded to three other carbon atoms.

Primary alcohol

OH group bonded to primary carbon atom.

Secondary alcohol

OH group bonded to secondary carbon atom.