AQA chemistry unit 1 definitions

The metals in group 2 of the periodic table. 

Pure elements which can exsist in different physical forms in which their atoms are arranged differently 

e.g. Diamond, Graphite and buckminsterfullerene are all allotropes of carbon.  

Describes the efficency of a chamical reaction by compairing the total number of atoms in the starting materials. it is defined by: 

mass of desired product product/ total mass of reactants    x100

a region of space around an atomic nucleus where there is a high probablilty of finding an electron. 

covalent bonding in which both the electrons in the bond come from one of the atoms in the bond. (also known as dative covalent bonding.)

Describes electrons that are spread over several atoms and help to bond them together. 

An intermolecular force that resu.ts from the attraction between molecules with permanate dipoles. 

The probablity of and electron being found in a particular volume of space.

A theory that explains the shapes of simple molecules by assuming that pairs of electrons around a central atom repel each other and therefore take up positions as far away as possible from each other in space.

The power of an atom to attract electrons in a covalent bond. 

The forces of attraction and repulsion between electrically charged particles. 

A vertical column of elements in the periodic table. the elements have similar properties because they have the same outer electron arrangement. 

A type of intermolecular force in which a hydrogen atom covalently bonded to an electronegative atom, interacts with another electronegative atom.

Chemical bond in which an electron or electrons are transferred from one atom to another, resulting in the formation of oppositely charged ions with electrostatic forces of attraction between them. 

The energy required to remove a mole of electrons from one mole of gaseous atoms or ions to produce one mole of postive ions. 

A regular three dimensional arrangement of atoms, ions or molecules. 

A pair of electrons in the outer shell of an atom that is not involved in bonding. Also called an unshared pair. 

Chemical bond in which outer electrons are spread over a lattice of metal ions in a delocalised system.   

in mass spectometery this is a molecule of the sample which has been ionised but which has not broken up during its flight through the instrument.  

Protons and neutrons- the subatomic particles found in the nulcei of atoms. 

The tiny postively charged centre of an atom composed of protons and neutrons.

A horisontal row of elements in the periodic table. There are trends in the properties of the elements as we cross a period. 

The regular recurrance of the properties of elements when they are arranged in atomic number order as in the periodic table. 

Describes a molecule in which the charge is not symmetrically distributed so that on area is slightly positively charged and the other slightly negatively charged. 

The number of protons in the nucleus of an atom, the same as the atomic number.  

Ar= average mass of an atom/ 1/12th mass of 1 atom of 12C 

Mr= average mass of entity  /  1/12th the mass of 1 atom of 12C

Average mass of a molecule  /   1/12th mass of 1 atom of 12C

Intermolecular force of attraction that is caused by instantaneous dipoles and acts between all atoms and molecules. 

a quantity of substance that contains the Avogadro number ( 6.022 x 10-23 ) of particles (e.g. atoms molecules or ions) 

A formula that tell us the number of atoms of each different element that make up a molecule of a compound. 

The simplest whole number ratio in which the atoms in a compound combine together. 

A hydrocarbon with C-C and C-H single bonds only, with the general formular CnH2n+2 

A set of organic compounds with the same funtional group. the compunds differ in length of their hydrocarbon chain. 

a reaction in which an atom or a group of atoms loses electrons. 

In a chemical reaction this is the actual amount of product produced divided by the theoretical amount (predicted from the chemical equation) expresssed as a percentage.  

ions tha6t are unchanged during a chemical reaction i.e, they take no part in the reaction 

Bonds are not shown but each carbon atom is written seperately with atoms or groups of atooms attached to it. 

e.g, butan-2-ol 

CH3CH2(OH)CH2CH3

a compound containing only hydrogen and carbon withonly C-C and C-H single bonds

i.e. one to which no more hydrogen can be added.  

show every bond.

one of two (or more) compounds with the same molecular formula but different structural formular 

i.e. the same atoms are arranged differently in space. 

the force that hold protons and neutrons together within the nucleus of the atom.