Glossary of Key Chemistry Terms and Concepts

chemestery

anhydrous

describes a substance that does not contain water

Avogadro constant

the number of atoms, molecules, or ions in a mole of any substance (i.e., 6.02 × 10-23 per mol)

burette

a long glass tube with a tap at one end and markings to show volumes of liquid; used to add precisely known volumes of liquids to a solution in a conical flask below it

concentration

the amount of a substance dissolved in a given volume of liquid

concordant

when you have two titration results that are within 0.1cm3 of each other. These precise results can then be used to calculate an accurate mean

end point

the point in a titration where the reaction is complete and titration should stop

hydrated

Describes a substance that contains water in its crystals

limiting reactant

the reactant in a chemical reaction that when used up causes the reaction to stop

mole

the amount of substance in the relative atomic or formula mass of a substance in grams

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

pipette

a glass tube used to measure accurate volumes of liquids

relative atomic mass Ar

the average mass of the atoms of an element compared with carbon-12 (which is given a 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 ratio shown in the chemical formula, of a substance

reversible reaction

a reaction in which the products can re-form the reactants

titration

a method for measuring the volumes of two solutions that react together

yield

the mass of product that a chemical reaction produces

alkali metal

elements in Group 1 of the periodic table

atom

the smallest part of an element that can still be recognised as that element

atomic number

the number of protons (which equals the number of electrons) in an atom. It is sometimes called the proton number

electron

a tiny particle with a negative charge. Electrons orbit the nucleus of atoms or ions in shells

electronic structure

a set of numbers to show the arrangement of electrons in their shells (or energy levels)

element

a substance made up of only one type of atom. An element cannot be broken down chemically into any simpler substance

group

all the elements in the columns (labelled 1 to 7 and 0) in the periodic table

halogens

the elements found in Group 7 of the periodic table

inert

unreactive

mass number

the number of protons plus neutrons in the nucleus of an atom

neutron

a dense particle found in the nucleus of an atom. It is electrically neutral, carrying no charge

noble gases

the very unreactive gases found in Group 0 of the periodic table. Their atoms have very stable electronic structures

nucleus (of an atom)

the very small and dense central part of an atom that contains protons and neutrons

periodic table

an arrangement of elements in the order of their atomic numbers, forming groups and periods

proton

a tiny positive particle found inside the nucleus of an atom

transition element

element from the central block of the periodic table