Core AS Definitions Flashcards
Element
A substance containing only one type of atom
Compound
A substance containing more than one type of atom chemically bonded to each other
Mixture
A combination of two or more substances that are not chemically bonded to each other
Molecule
A small number of atoms joined together with covalent bonds
Particle
A general term used to describe any small portion of matter
Atom
The smallest component of an element
Atomic number
The number of protons in the nucleus of an atom
Mass number
The mumber of protons and neutrons in the nucleus of an atom
Isotopes
Atoms of the same element with a different number of neutrons and different masses
Relative isotopic mass
The mass of one atom of an isotope compared with 1/12th of the mass of one atom of C-12
Relative atomic mass
The weighted mean mass of an atom of an element compared with 1/12 of the mass of one atom of C-12
Mole
The amount of substance containing as many particles as there are carbon atoms in exactly 12g of C-12
Avogadro’s constant
The number of particles per mole of a substance (6.02×10^23)
Molar mass
The mass per mole of a substance (gmol^-1)
Empirical formula
The simplest whole number ratio of atoms of each element present in a compound
Molecular formula
The actual number of atoms of each element present in a compound
Strong acid
A proton donor, which is fully dissociated in aqueous solution
Weak acid
A proton donor which is partially dissociated in aqueous solution
Neutralisation
The reaction of an acid with a base to form a salt
Base
A proton acceptor
Alkali
A soluble base that releases OH- ions when in aqueous solution
Salt
A compound produced when one or more H+ ions from an acid is replaced by a metal ion or another positive ion
Water of crystallisation
The water present in a compound giving the compound a crystalline appearance
Anhydrous
When all the waters of crystallisation have been removed from a compound
Hydrated
When water of crystallisation is present in a compound
Atomic orbital
A region around the nucleus of an atom that can hold up to two electrons with opposite spins
s/p/d block element
Highest energy electron is in an s/p/d sub-shell/orbital
Metallic bond
Strong electrostatic attraction between lattice of metal cations and delocalised electrons
Ionic bond
The strong electrostatic attraction between lattice of positive and negative ions
Covalent bond
The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
Dative covalent (co-ordinate) bond
The sharing of a pair of electrons between two atoms where only one of the atoms supplies both the electrons shared
Electronegativity
The ability of an atom to attract the bonding pair of electrons toward itself in a covalent bond
Periodicity
The repeating pattern of trends in physical and chemical properties across different periods
Hydrogen bonding
Intermolecular bonding between the electron deficient H atom of -NH, -OH, or HF on one molecule and a lone pair of electrons on the highly electronegative N, O, or F atom of another molecule
