Flashcards in A level Chemistry Deck (73):
A substance which cannot be broken down by any chemical process. All the atoms within it have the same atomic number (a material with only one type of atom).
An electrically charged particle formed from an atom or group of atoms which have lost or gained electrons.
The number of protons + the number of neutrons in the nucleus.
The number of protons in an atom
Atoms which have the same number of protons but different numbers of neutrons. They have the same atomic number but different neutron numbers.
Relative Isotopic Mass
The mass of an atom of a particular isotope of an element relative to 1/12 of the mass of carbon–12 atom, defined as 12 exactly.
Relative Atomic Mass
The weighted average mass of atoms of an element in their natural relative isotopic abundance compared to the carbon 12 isotope taking the mass of 12 C =
An electrostatic attraction between oppositely charged positive cations and negative anions. It is usually formed by electron transfer from a metal atom to a non metal.
A shared pair of electrons one from each donor atom
The electrostatic attraction between the nuclei and the bonding pair of electrons which holds the 2 nuclei together.
The distance between the nuclei of the two atoms that are covalently bonded together.
Double Covalent Bond
A covalent bond in which two pairs of electrons are shared between two atoms.
Dative Covalent Bond
Is a shared pair of electrons both from one donor atom
Two or more forms of the same element in which the atoms or molecules are arranged in different ways
The electrostatic attractions between positive metal
cations and the delocalised electrons.
Valence Shell Electron Pair Repulsion (VSEPR) Theory
- Bonding pairs of electrons around a central atom repel each other and arrange themselves as far apart around the central atom to minimise repulsion
-lone pairs of electrons are held more closely to the central atom and so exert a greater repelling effect than bonding pairs. This reduces the bond angle by approx 2 o per lone pair.
The angle between two covalent bonds in a molecule or giant covalent structure
The distance between the nuclei of two atoms linked by one or more covalent bonds.
Polar Covalent Bond
A covalent bond where the bonding pair of electrons are not shared equally by the two atoms in the bond.The shared electrons are attracted towards the atom with the stronger pull from the nucleus which is described as more electronegative The bonds have a slightly positive pole + at one end and a negative one - at the other.
A measure of its ability to attract the shared pair of
electrons in a covalent bond. It is a comparative scale based on Fluorine = 4.0
A particularly strong permanent dipole-permanent dipole attraction between the lone pair of electrons on a very electronegative atom (N, O or F) and a hydrogen atom directly covalently bonded to another very electronegative N, O or F atom.
The smallest uncharged particle of an element.
Made up of two or more elements chemically joined together
The amount of substance containing the Avogadro number of atoms, molecules or groups of ions. Where Avogadro’s number is 6.023 * 10^23 mol -1. Or The amount of substance containing as many particles as there are carbon atoms in 12g of 12 C
The simplest whole number ratio of the atoms of each element in the substance. It is also the simplest whole number ratio of moles of atoms in a substance.
Shows the number of atoms of each element in
Parts per Million
The mass of solute per million grams of solvent.
Relative Formula Mass
The weighted mean mass of a formula unit compared to the carbon-12 isotope taking 12 C = 12.0000.
The mass of one mole of any substance in g/mol.
The number of atoms in exactly 12g of 12 C which is 6.02 * 10^23 .
An inaccuracy in the results of the experiment which
is caused by a limitation of the method or equipment being used.
These are the inaccuracies of any measurement taken which involves a piece of measuring equipment and their size depends on the equipment used.
These are due to the problems with the method used which affect the results but cannot be measured.
Molar Volume of a Gas
The volume occupied by 1 mole of the gas under specified conditions of temperature and pressure.
The substance that determines the theoretical yield of a product in a reaction.
Is defined as % yield = (actual yield/theoretical yield) x 100
% atom economy
(mass of desired product from equation/total mass of products from equation)x 100
A solution with an accurately known concentration. A standard solution is prepared by taking a known mass of solute and making this up to a known volume of solution in a volumetric flask.
Concentration/Molarity in mol/dm^3
number of moles *(1000cm^3/volume in cm^3)
When a species loses one or more electrons
When a species gains one or more electrons
Reactions which involve transfer of electrons
Brings about an oxidation. It itself is reduced
Brings about a reduction. It itself is oxidised
The charge the species in a molecule or ion would have if the bonding was 100% ionic
The simultaneous oxidation and reduction of atoms of the same elements
First ionisation Energy
The first ionisation energy is defined as the energy required to remove one mole of electrons from one mole of gaseous neutral atoms to form one mole of gaseous ions with a charge of +1
Properties which show a gradual change/trend across a period which repeats from period to period. It due to this repeating pattern from left to right that the table in known as the periodic table
Compounds containing carbon and hydrogen atoms only
A family of compounds with the same functional group, which differ in formula by CH 2 from the next member.
The atom or group of atoms responsible for the chemical behaviour of the molecule
Are made up of chains of carbon atoms which may be straight or branched (i.e. they do not contain rings)
Are made up of closed rings of carbon atoms.
Contain only single covalent bonds. They have the maximum number of hydrogen atoms.
Contain double or triple bonds which can add more
hydrogen atoms to form additional C-H bonds.
Occurs when two or more compounds have the same molecular formula but different structural formulae.
Cracking is the breakdown of molecules into
shorter ones by heating with a catalyst.
The conversion of straight chained hydrocarbons into branched and cyclic hydrocarbons by heating with a platinum catalyst.
Is the term used to describe the breaking of a covalent bond so that the bonding electrons are shared equally between the atoms involved. It is represented using half-headed curly arrows.
Half Headed Curly Arrows
Show the movement of one electron precisely from
the covalent bond to the atom to which the electron moves.
Molecular fragments or atoms with one unpaired electron. They are highly reactive.
Where one atom or group of atoms replaces another atom or group of atoms
Something that could cause harm depending on circumstances
The chance or probability that harm will occur
Where one or more groups are added onto a molecule to give a single product
(It usually converts an unsaturated compound into a saturated compound.)
An electron deficient species with a vacant orbital. They are often positively charged. They react by accepting a pair of electrons forming a new covalent bond.
Heterolytic Bond Fission
This results in the production of two different (hetero) species.
A: B ---> A: - + B + or A :B ---> A + + :B -
The covalent bond breaks so that both the bonding electrons go to either A or B. It results in the formation of oppositely charged ions.
A reaction in which water or a hydroxide group replace an atom in a molecule with an -OH group
The removal of one or more groups or atoms from adjacent C atoms forming an unsaturated molecule.
The removal of a water molecule – water is the only inorganic product formed in the reaction
The heat change when the reaction is carried
out at constant pressure. It is given the symbol ΔH
Specific Heat Capacity
The enthalpy in joules/KJ which heats 1g/Kg of the substance by 1 o C/K