1.1 atomic model, symbols, relative atomic mass

• An element is a substance made up of one type of atom
• An atom is a particle made up of electrons, protons, and neutrons. They make up everything.
• A compound is a substance made up of more than one type of element, chemically bonded together.
• A salt is a compound formed when the H+ ions in an acid are replaced with a metal or ammonia.
• An acid is a substance that has a pH below 7. They donate H+ ions to the solution.
• A base is a substance that neutralises acids by accepting H+ ions.
• An alkali is a substance that has a pH of above 7. They release OH- ions in a solution.
• an ion is an atom which has gained or lost electrons to form a full outer shell.