Question | Answer |
Relative isotopic mass | The mass of an atom of the isotope, compared with one-twelfth of the mass of carbon-12. |
Relative molecular mass | The weighted mean mass of a molecule, compared with one-twelfth of the mass of carbon-12. |
Anhydrous | A molecule containing no water molecules |
Simple molecular lattice | A 3-D structure of molecules, bonded together by weak intermolecular forces. |
Shell | A group of atomic orbitals with the same principal quantum number/same main energy level. |
Alkali | A type of base that dissolves in water, forming hydroxide ions. |
1st Ionisation energy | The energy required to remove one electron in each atom in one mole of gaseous atoms, to form one mole of gaseous 1+ ions. |
Ion | A positively or negatively charged atom. |
Acid | A proton donor |
Intermolecular force | An attractive force between neighbouring molecules. |
2nd Ionisation energy | The energy required to remove an electron from each ion in one mole of gaseous 1+ ions, to form one mole of gaseous 2+ ions. |
Successive ionisation energies | A measure of the energy required to remove each electron in turn. |
Hydrogen bond | A strong dipole dipole set traction, between an electron deficient hydrogen atom on one molecule, and a highly electronegative molecule (O,N) on another. |
Period | A horizontal row of elements in the periodic table, showing trends. |
Salt | A chemical compound formed from an acid, when a H+ ion from the acid has been replaced by a metal ion or another positive ion. |
Periodicity | A regular periodic variation of properties of elements with atomic number and position in the periodic table. |
Hydrated | Crystalline and containing water molecules |
Group | A vertical column in the periodic table, involving elements with the same number of electrons in their outer shell, and similar chemical properties. |
Reduction | A gain of electrons and loss in oxidation number. |
Oxidation | A loss in electrons and gain in oxidation number |
Electronegativity | A measure of the attraction of a bonded atom, for the pair of electrons in a covalent bond. |
Reducing agent | A reagent that reduces/adds electrons to another species. |
Giant metallic lattice | A three dimensional structure of positive ions and delocalised electrons, held together by strong metallic bonds. |
Oxidising agent | A reagent that increases/removes electrons from mother species. |
Electron configuration | The arrangement of electrons in an atom. |
Giant ionic lattice | A three dimensional structure of positive and negative ions held together by strong ionic bonds. |
Redox reaction | A reaction involving both reduction and oxidation. |
Principal quantum number | A number representing the relative overall energy level for each orbital, which increases with distance from the nucleus. |
Thermal decomposition | The breaking up of a chemical substance, with heat into at east two different substances. |
Oxidation number | A measure of the number of electrons that an atom uses to bond with atoms of another element. |
Giant covalent bond | A three dimensional structure of atoms, bonded together by strong covalent bonds. |
Van der waals forces | Very weak attractive forces between induced dipoles in neighbouring molecules. |
Sub-shell | A group of the same type of atomic orbitals e.g. s,p,d,f |
Molecule | A small group of atoms held together by a covalent bond |
Empirical formulae | The simplest, whole number ratio of atoms of each element present in. Compound. |
Polar molecule | A molecule that has an overall dipole, taking into account any dipoles across bonds. |
Polar covalent bond | A bond with a permanent dipole. |
Electron shielding | The repulsion between electron in different inner shells. |
Permanent dipole-dipole force | An attractive force between permanent dipoles in neighbouring polar molecules. |
Permanent dipole | A small charge difference across a bond resulting from a difference in electronegativities of the bonded atoms. |
Disproportionation | The oxidation and reduction of the same element in a redox reaction. |
Displacement reaction | A reaction in which a more active element displaces a less active element from an aqueous solution of the latter's ions. |
Delocalised electrons | Electrons that are shared between more than two atoms |
Dative covalent bond | A shared pair of electrons which has been provided by one of the bonding atoms only. |
Covalent bond | A bond formed by a shared pair of electrons |
Concentration | The amount of solute, in moles per 1000cm3 of solution. |
Compound | A substance formed by two or more chemically bonded elements in a fixed ratio, usually shown by a chemical formula |
Cation | A positively charged ion |
Molecular formula | The number of atoms of each element in a molecule. |
Mole | The amount of any substance containing as many particles as there are carbon atoms in exactly 12g of carbon-12 isotope. |
Molar volume | The volume per mole of a gas. |
Catalyst | A substance that increases the rate of a chemical reaction by providing a smaller activation energy and alternative reaction pathway, and is not used up in the process. |
Molar mass (M) | The mass per mole of a substance. |
Base | A species that is a proton acceptor |
Metallic bond | The electrostatic attraction between fixed positive ions and a sea of delocalised electrons. |
Mass number | The number of protons and neutrons in the nucleus. |
Avogadro constant | The number of atoms per mole of the carbon-12 isotope 6.023x10 to the power of 23 |
Lone pair | An outer shell pair of electrons that are not involved in chemical bonding. |
Atomic number | The number of protons in the nucleus |
Limiting reagent | The substance in a chemical reaction that runs out first. |
Stoichiometry | The molar relationship between the relative quantities of substances taking part in a reaction. |
Standard solution | A solution of known concentration. (Normally used in titrations) |
Species | Any type of particle that takes part in a reaction. |
Isotopes | Atoms of the same element with different mass numbers and different number of neutrons in the nucleus (but the Same proton number) |
Orbital | A region of space within an atom that can hold up to two electrons with opposite spins. |
Relative atomic mass | The weighted mean mass of an atom of an element, compared with one-twelfth of the mass of carbon-12 which is taken as 12 exactly |
Spectator ions | Ions that are present, but do it take part in the chemical reaction. |
Ionic bond | The electrostatic attraction between oppositely charged ions. |
Relative formula mass | The weighted mean mass of a formula unit, compared with one-twelfth of the mass of carbon-12. |
Anion | A negatively charged ion |
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