Question | Answer |
Atomic Number | The number of protons (which equals the number of electrons) in an atom. It is sometimes called the proton number. |
Empirical Formula | The simplest ratio of elements in a compound. |
Isotope | Atom that has the same number of protons but a different number of neutrons. i.e. the same atomic number but a different mass number. |
Mass Number | The number of protons plus the number of neutrons in the nucleus of an atom. |
Mole | The amount of substance in the relative atomic or formula mass of a substance in grams. |
Molecular Formula | The chemical formula that shows the actual numbers of atoms in a particular molecule (e.g. C2H4). |
Percentage Yield | The actual mass of product collected in a reaction divided by the maximum mass that could have been formed in theory, multiplied by 100. (i.e. (actual yield/theoretical yield) x 100) |
Relative Atomic Mass,Ar | The average mass of the atoms of an element compared to carbon-12 (which is given the mass of exactly 12). The average mass must take into account the proportions of the naturally occurring isotopes of the element. |
Relative Formula Mass, Mr | The total of the relative atomic masses, added up in the ration shown in the chemical formula, of a substance. |
Reversible Reaction | A reaction in which the products can re-form the reactants. |
Symbol Equation | A balanced chemical equation showing the formula for each reactant and product in the reaction e.g. H2 + Cl2 = 2HCl |
Word Equation | A way of describing what happened in a chemical reaction by showing the names of all the reactants and products they form. |
Chromatography | The process by which small amounts of dissolved substances are separated by running a solvent along a material such as absorbent paper. |
Gas Chromatography | The process of separating the components in a mixture by passing the vapours through a column and detecting them as they leave the column at different times. |
Equilibrium | The point in a reversible reaction in which the forward and backward rates of reaction are the same. Therefore, the amount of substances present in the reacting mixture remain constant. |
Mass Spectrometer | A machine that can be used to analyse small amounts of a substance to identify it and to find its relative molecular mass. |
Molecular Ion Peak | The peak on the mass spectrum of a substance which tells us the relative molecular mass of the substance. The peak is produced by the heaviest positive ion shown on the mass spectrum. |