Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Glossary acid A species that is a proton donor. alkali A type of base that dissolves in water forming hydroxide ions, OH–(aq) ions. anhydrous A substance that contains no water molecules. anion A negatively charged ion. atomic orbital A region within an atom that can hold up to two electrons, with opposite spins. atomic (proton) number The number of protons in the nucleus of an atom. Avogadro constant, NA The number of atoms per mole of the carbon-12 isotope (6.02 × 1023 mol–1). base A species that is a proton acceptor. cation A positively charged ion. concentration The amount of solute, in mol, per 1 dm3 (1000 cm3) of solution. coordinate bond A shared pair of electrons which has been provided by one of the bonding atoms only; also called a dative covalent bond. © Pearson Education Ltd 2008 This document may have been altered from the original 1 covalent bond A bond formed by a shared pair of electrons. dative covalent A shared pair of electrons which has been provided by one of the bonding atoms only; also called a coordinate bond. delocalised electrons Electrons that are shared between more than two atoms. displacement reaction A reaction in which a more reactive element displaces a less reactive element from an aqueous solution of the latter’s ions. disproportionation The oxidation and reduction of the same element in a redox reaction. electron configuration The arrangement of electrons in an atom. electronegativity A measure of the attraction of a bonded atom for the pair of electrons in a covalent bond. electron shielding The repulsion between electrons in different inner shells. Shielding reduces the net attractive force from the positive nucleus on the outer-shell electrons. empirical formula The simplest whole-number ratio of atoms of each element present in a compound. giant covalent lattice A three-dimensional structure of atoms, bonded together by strong covalent bonds. © Pearson Education Ltd 2008 This document may have been altered from the original 2 giant ionic lattice A three-dimensional structure of oppositely charged ions, bonded together by strong ionic bonds. giant metallic lattice A three-dimensional structure of positive ions and delocalised electrons, bonded together by strong metallic bonds. group A vertical column in the Periodic Table. Elements in a group have similar chemical properties and their atoms have the same number of outer shell electrons. hydrated Crystalline and containing water molecules. hydrocarbon A compound of hydrogen and carbon only. hydrogen bond A strong dipole–dipole attraction between an electron-deficient hydrogen atom (O–Hδ+ or N–Hδ+) on one molecule and a lone pair of electrons on a highly electronegative atom (H–O:δ– or H– N:δ–) on a different molecule. intermolecular force An attractive force between neighbouring molecules. Intermolecular forces can be van der Waals’ forces (induced dipole–dipole forces), permanent dipole–dipole forces or hydrogen bonds. ion A positively or negatively charge atom or (covalently bonded) group of atoms (a molecular ion). ionic bonding The electrostatic attraction between oppositely charged ions. (first) ionisation energy The energy required to remove one electron from each ion in one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions. © Pearson Education Ltd 2008 This document may have been altered from the original 3 (second) ionisation energy The energy required to remove one electron from each ion in one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions. (successive) ionisation energy A measure of the energy required to remove each electron in turn, e.g. the second ionisation energy is the energy required to remove one electron from each ion in one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions. isotopes Atoms of the same element with different numbers of neutrons and different masses. limiting reagent The substance in a chemical reaction that runs out first. lone pair An outer-shell pair of electrons that is not involved in chemical bonding. mass (nucleon) number The number of particles (protons and neutrons) in the nucleus. metallic bond The electrostatic attraction between positive metal ions and delocalised electrons. molar mass, M The mass mole of a substance. The units of molar mass are g mol–1. molar volume The volume per mole of a gas. The units of molar volume are dm3 mol–1. At room temperature and pressure the molar volume is approximately 24.0 dm3 mol–1. mole The amount of any substance containing as many particles as there are carbon atoms in exactly 12 g of the carbon-12 isotope. © Pearson Education Ltd 2008 This document may have been altered from the original 4 molecular formula The number of atoms of each element in a molecule. molecule A small group of atoms held together by covalent bonds. oxidation Loss of electrons or an increase in oxidation number. oxidation number A measure of the number of electrons that an atom uses to bond with atoms of another element. Oxidation numbers are derived from a set of rules. oxidising agent A reagent that oxidises (takes electrons from) another species. period A horizontal row of elements in the Periodic Table. Elements show trends in properties across a period. periodicity A regular periodic variation of properties of elements with atomic number and position in the Periodic Table. permanent dipole A small charge difference across a bond resulting from a difference in electronegativities of the bonded atoms. permanent dipole– dipole force An attractive force between permanent dipoles in neighbouring polar molecules. pi-bond (π-bond) The reactive part of a double bond formed above and below the plane of the bonded atoms by sideways overlap of p-orbitals. © Pearson Education Ltd 2008 This document may have been altered from the original 5 polar covalent bond A bond with a permanent dipole. polar molecule A molecule with an overall dipole, taking into account any dipoles across bonds. precipitation reaction The formation of a solid from a solution during a chemical reaction. Precipitates are often formed when two aqueous solutions are mixed together. principal quantum number, n A number representing the relative overall energy of each orbital, which increases with distance from the nucleus. The sets of orbitals with the same n value are referred to as electron shells or energy levels. redox reaction A reaction in which both reduction and oxidation take place. reducing agent A reagent that reduces (adds electron to) another species. reduction Gain of electrons or a decrease in oxidation number. relative atomic mass, Ar The weighted mean mass of an atom of an element compared with one-twelfth of the mass of an atom of carbon-12. relative formula mass The weighted mean mass of a formula unit compared with onetwelfth of the mass of an atom of carbon-12. relative isotopic mass The mass of an atom of an isotope compared with one-twelfth of the mass of an atom of carbon-12. © Pearson Education Ltd 2008 This document may have been altered from the original 6 relative molecular mass, Mr The weighted mean mass of a molecule compared with onetwelfth of the mass of an atom of carbon-12. Salt A chemical compound formed from an acid, when a H+ ion from the acid has been replaced by a metal ion or another positive ion, such as the ammonium ion, NH4+. shell A group of atomic orbitals with the same principal quantum number, n. Also known as a main energy level. simple molecular lattice A three-dimensional structure of molecules, bonded together by weak intermolecular forces. spectator ions Ions that are present but take no part in a chemical reaction. standard solution A solution of known concentration. Standard solutions are normally used in titrations to determine unknown information about another substance. sub-shell A group of the same type of atomic orbitals (s, p, d or f) within a shell. thermal decomposition The breaking up of a chemical substance with heat into at least two chemical substances. van der Waals’ forces Very weak attractive forces between induced dipoles in neighbouring molecules. volatility The ease that a liquid turns into a gas. Volatility increases as boiling point decreases. © Pearson Education Ltd 2008 This document may have been altered from the original 7 water of crystallisation Water molecules that form an essential part of the crystalline structure of a compound. © Pearson Education Ltd 2008 This document may have been altered from the original 8