Module 2 - Keywords Flashcards
Isotopes
Atoms of the same element with different numbers of nuetrons and different masses but the same number of protons and electrons
Relative isotopic mass
The mass of an isotope compared with 1/12th the mass of carbon-12
Relative atomic mass
Weighted mean mass of an atom compared with 1/12 the mass of carbon-12
Relative molecular mass, Mr
Mass of a molecule compared with 1/12th the mass of carbon-12
Mole
The unit for an amount of substance (6.02x1023 mol-1)
Avogadro constant
The number of particles per mole, 6.02x1023 mol-1
Molar mass
Mass per mole, units: gmol-1
Mass spectrometry
Method used to determine the relative abundances of different isotopes
Empirical formula
Simplest whole number ratio of atoms of each element present in a compound
Molecular formula
Number and type of atoms of each element in a molecule
Anhydrous
Contains no water
Hydrated
Contains water of crystallisation
Ideal gas equation
pV=nRT
Stoichiometric relationships
The whole number relationships between particles of reactants and products
Percentage yield
actual yield/expected yield x100
Atom economy
Useful products/total product x100
Acid
Proton donor, release H+ in aqueous solution
Base
Proton acceptor
Alkalis
A substance that releases OH- ions in aqueous solution
Neutralisation reaction
A reaction of H+(aq) + OH-(aq) → H2O(l)
Titration
The slow addition of one solution of a known concentration to a known volume of another solution of unknown concentration until the end point
Strong acid
An acid that completely dissociates in water HA → H+ + A-
Weak acid
An acid that only partially dissociates in water HA ⇌ H+ + A-
Dilute acid
An acid with only a few particles dissolved per litre (e.g. 0.01 moldm-3)
Concentrated acid
An acid with lots of particles dissolved per litre (e.g. 50 moldm-3)
Oxidation number
A measure of the number of electrons involved in bonding. Used to work out what has been oxidised/reduced
Oxidation
Loss of electrons, increase in oxidation mumber, adding oxygen
Reduction
Gain of electrons, decrease in oxidation number, removing oxygen
Redox
A reaction in which one substance is oxidised and another reduced
Salt
A compound formed when the hydrogen in an acid is replaced by a metal
Orbital
A region around the nucleus that can hold up to 2 electrons, with opposite spins
Subshell
Orbitals which have the equivalent energy levels. s subshells contain 1 orbital, p subshells contain 3 orbitals, d subshells contain 5 orbitals
Electron configuration
Shows how the electrons are arranged in the subshells
Ionic bond
Electrostatic attraction between positive and negative ions
Giant ionic lattices
Structure resulting from oppsoitely charges ions strongly attracted in all directions e.g. NaCl
Covalent bond
The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
Dative covalent bond
A shared pair of electrons where both electrons originated from the same atom
Average bond enthalpy
A measurement of covalent bond strength. It’s the energy changes associated with breaking 1 mole of bonds in gaseous molecules
Electron pair repulsion theory
The idea that electron pairs repel and so affect the shape of the particles. Non bonding pairs (lone pairs) repel more than bonded pairs
Linear
Shapes caused by having 2 bonding pairs and 0 non bonding electron pairs, which repel as far as possible. Bond angle: 180°
Non linear
Shape caused by having 2 bonding and 1/2 non bonding electron pairs which repel as far as possible. The non bonding pairs repel more than bonding pairs. Bond angle: 118°/104.5°
Trigonal planar
Shape caused by having 3 bonding and 0 non bonding electron pairs which repel as far as possible. Bond angle: 120°
Pyramidal
Shape caused by having 3 bonding and 1 non bonding electron pairs which repel as far as possible. The non bonding pairs repel more than bonding pairs. Bond angle: 107°
Tetrahedral
Shape caused by having 4 bonding and 0 non bonding electron pairs which repel as far as possible. Bond angle: 109.5°
Octahedral
Shape caused by having 6 bonding and 0 non bonding electron pairs which repel as far as possible. Bond angle: 90°
Electronegativity
The ability of an atom to attract the bonding electrons in a covalent bond
Polar bond
A covalent bond in which there is a permanent dipole due to different electronegativites of the bonded atoms
Dipole
Having a positive and a negative end
Induced dipole
An instantaneous dipole caused by dipoles on neighbouring molecules
London forces
Induced dipole-dipole interactions between molecules
Hydrogen bond
Intermolecular bonding between molecules containing N, O or F and the H atom of -NH, -OH or HF