Fichas
Unit 1 definitions
Fichas del conjunto (67)
- 1What is an isotope?An atom of the same element with a different number of neutrons.
- 2What is atomic (proton) number?The number of protons in the nucleus of an atom.
- 3What is mass (nucleon) number?The number of particles (protons and neutrons) in the nucleus.
- 4What is an ion?A positively or negatively charged atom or group of atoms.
- 5What is relative isotopic mass?The mass of an atom of an isotope compared with one twelfth of the mass of an atom of Carbon-12.
- 6What is relative atomic mass?The weighted mean mass of an atom of an element compared with one twelfth of the mass of an atom of Carbon-12.
- 7What is relative molecular/relative formula mass?The weighted mean mass of a molecule/formula unit compared with one twelfth of the mass of an atom of Carbon-12.
- 8What is amount of substance?The quantity whose unit is the mole. It is used as a means of counting atoms.
- 9What is the Avogadro constant?The number of atoms per mole of the Carbon-12 isotope.
- 10What is a mole?The amount of any substance containing as many particles as there are carbon atoms in exactly 12g of the Carbon-12 isotope.
- 11What is molar mass?The mass per mole of a substance (units g/mol).
- 12What is empirical formula?The simplest whole-number ratio of atoms of each element present in a compound.
- 13What is a molecule?A small group of atoms held together by covalent bonds.
- 14What is molecular formula?The actual number of atoms of each element in a molecule.
- 15What is molar volume?The volume per mole of a gas. At room temperature and pressure, the molar volume is approximately 24.0 dm^3 mol^-1.
- 16What is concentration?The amount of solute, in mol, dissolved per litre of solution.
- 17What is a standard solution?A solution of known concentration. They are normally used in titrations to determine unknown information about another substance.
- 18What is a species?Any type of particle that takes part in a chemical reaction.
- 19What is stoichiometry?The molar relationship between the relative quantities of substances taking part in a reaction.
- 20What is an acid?A species that is a proton donor.
- 21What is a base?A species that is a proton acceptor.
- 22What is an alkali?A type of base that dissolves in water forming hydroxide ions.
- 23What is a salt?Any chemical compound formed from an acid when a H+ ion from the acid has been replaced by a metal ion or another positive ion.
- 24What is a cation?A positively charged ion.
- 25What is an anion?A negatively charged ion.
- 26What does hydrated mean?It refers to a crystalline compound containing water molecules.
- 27What does anhydrous mean?It refers to a substance that contains no water molecules.
- 28What is water of crystallisation?It refers to water molecules that form an essential part of the crystalline structure of a compound.
- 29What is an oxidation number?A measure of the number of electrons that an atom uses to bond with atoms of another element. They are derived from a set of rules.
- 30What is oxidation?Loss of electrons or increase in oxidation number.
- 31What is reduction?Gain of electrons or a decrease in oxidation number.
- 32What is a reducing agent?A reagent that reduces (adds electrons to) another species.
- 33What is an oxidising agent?A reagent that oxidises (takes electrons from) another species.
- 34What is first ionisation energy of an element?The energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions.
- 35What is 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.
- 36What are successive ionisation energies?A measure of the energy required to remove each electron in turn.
- 37What is a shell?A group of atomic orbitals with the same principal quantum number, n. Also known as the main energy level.
- 38What is principal quantum number?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.
- 39What is an atomic orbital?A region within an atom that can hold up to two electrons, with opposite spins.
- 40What is a sub-shell?A group of the same type of atomic orbitals (s, p, d or f) within a shell.
- 41What is electron configuration?The arrangement of electrons in an atom.
- 42What is a compound?A substance formed from two or more chemically bonded elements in a fixed ratio, usually shown by a chemical formula.
- 43What is an ionic bond?The electrostatic attraction between oppositely charged ions.
- 44What is a giant ionic lattice?A three-dimensional structure of oppositely charged ions, held together by strong ionic bonds.
- 45What is a group?A vertical column in the Periodic Table. Elements in the same group have similar chemical properties and their atoms have the same number of outer-shell electrons.
- 46What is a covalent bond?A bond formed by a shared pair of electrons.
- 47What is a lone pair?An outer-shell pair of electrons that is not involved in chemical bonding.
- 48What is a dative covalent/coordinate bond?A shared pair of electrons which has been provided by one of the bonding atoms only.
- 49What is electronegativity?A measure of the attraction of a bonded atom for the pair of electrons in a covalent bond.
- 50What is a permanent dipole?A small charge difference across a bond that results from a difference in the electronegativities of the bonded atoms.
- 51What is a polar covalent bond?A covalent bond with a permanent dipole.
- 52What is a polar molecule?A molecule with an overall dipole, when you take into account any dipoles across the bonds.
- 53What is an intermolecular force?An attractive force between neighbouring molecules.
- 54What is a permanent dipole-dipole force?A weak attractive force between permanent dipoles in neighbouring polar molecules.
- 55What are van der Waals' forces?Attractive forced between induced dipoles in neighbouring molecules.
- 56What is a hydrogen bond?A strong dipole-dipole attraction between an electron deficient hydrogen atom on one molecule and a lone pair of electrons on a highly electronegative atom on a different molecule.
- 57What is metallic bonding?The electrostatic attraction between positive metal ions and delocalised electrons.
- 58What are delocalised electrons?Electrons that are shared between more than two atoms.
- 59What is a giant metallic lattice?A three-dimensional structure of positive ions and delocalised electrons, bonded together by strong metallic bonds.
- 60What is a simple molecular lattice?A three-dimensional structure of molecules, bonded together by weak intermolecular forces.
- 61What is a giant covalent lattice?A three-dimensional structure of atoms, bonded together by strong covalent bonds.
- 62What is a period?A horizontal row of elements in the Periodic Table. Elements show trends in properties across a period.
- 63What is periodicity?A regular periodic variation of properties of elements with atomic number and position in the Periodic Table.
- 64What is thermal decomposition?The breaking up of a chemical substance with heat into at least two chemical substances.
- 65What is a displacement reaction?A reaction in which a more-reactive element displaces a less-reactive element from an aqueous solution of the latter's ions.
- 66What is disproportionation?The oxidation and reduction of the same element in a redox reaction.
- 67What is a 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.
Información
- Descripción
- AS Level OCR A Chemistry
- Creado por
- Steph Keogh
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