key definitions - atomic structure

• atom - the smallest piece of an element that can still be recognised as that element
• atomic number - the total number of protons in the nucleus of an atom
• mass number - the total number of protons and neutrons in the nucleus of an atom
• electron - a negatively charged sub-atomic particle outside the nucleus of an atom
• neutron - a neutral sub-atomic particle present in the nucleus of an atom
• proton - a positively charged sub-atomic particle found in the nucleus of an atom
• a compound is a substance made up of two or more different atoms chemically bonded together
• element - a substance containing atoms with the same atomic number
• mixture - 2 or more substances not chemically bonded together which can be separated
• molecule - a group of atoms chemically bonded together
• ion - an atom or group of atoms that have lost or gained electrons
• isotopes - atoms of the same element that have the same number of protons but a different number of neutrons
• periodic table - a table in which all the elements are arranged in order of increasing atomic number and elements with similar properties are placed in vertical groups
• relative atomic mass - the relative atomic mass of an element is the weighted average mass of the isotopes of the element relative to 1/12 of a carbon 12 atom