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. Most metals have a tendency to lose electrons to form positive ions.

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 and has a tendency to gain electrons to form negative ions.

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. Metals have high melting points and high conductivities.

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. Usually measured as the half-distance between the nuclei of two of the same atoms bonded together.

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. The greater the number of electrons removed, the smaller the ionic radius.

Periodicity of Ionic radius for positive 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. The greater the number of electrons gained, the larger the ionic radius.

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. Since electrons in higher energy levels have weaker attraction to the nucleus, ionization energy decreases. 

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 going down a group: The absolute value for first electron affinity generally decreases going down a group (lower affinity for gaining an electron), 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.

Periodicity of electron affinity going across a period: Absolute value for first electron affinity generally increases going across a period (higher affinity for gaining an electron) 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.

Periodicity of electronegativity going down a group: Electronegativity values generally decrease down a group. Atomic radius increases down a group from additional energy levels. Weaker attraction between the nucleus and the shared pair of electrons

Periodicity of electronegativity going across a period: Electronegativity values generally increase going across a period. Effective nuclear charge increases going across a period. 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.

Periodicity of metallic character: Increases across a period, decreases down the group

Periodicity of non-metallic character: Decreases across a period, increases down the group

General trend of reactivity for 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. Easier for elements with lower ionisation energy to transfer the outer valence electron to water increasing reactivity with water.

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.

General trend of reactivity for group 17 halogens in displacement reactions: 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.

The two major global concerns of acidic non-metal oxides: Ocean acidification and acid rain

Why is ocean acidification a threat to marine life?: 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. This weakens their structures, disrupts marine food chains, and threatens biodiversity.

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. 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 single carbon to carbon bonds.

Alkenes: A class of organic compounds double 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 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 compounds such as aldehydes and ketones have not only London dispersion forces acting between their molecules but also dipole–dipole attractions. This results in these compounds having higher boiling points than non-polar organic compounds of similar molar mass.

Compounds with either N–H or O–H bonds, such as the alcohols, carboxylic acids and amides, have hydrogen bonds acting between their molecules. Because hydrogen bonds are the strongest type of intermolecular force, these compounds tend to have higher boiling points and are less volatile.

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

Tertiary alcohol: OH group bonded to tertiary carbon atom

Primary amine: Only one hydrogen replaced with an alkyl group

Secondary amine: Only two hydrogens replaced with an alkyl group

Tertiary amine: All hydrogens replaced with an alkyl group