Elements

• Each atom is made up of protons, neutrons and electrons.
• All substances are made up of tiny particles of matter called atoms.
• Protons and Neutrons are located in the centre of the atom (nucleus), whereas electrons are located in shells around the nucleus.
• An element is a substance that cannot be broken down into simpler substances by chemical means. They are made of atoms.
• Elements are all found on the periodic table. They have have their own unique symbol.
• Atoms can gain or lose electrons to form ions.
• Ions have a positive charge if they have lost one or more electrons, and a negative charge if they have gained one or more electrons.
• Molecules are two or more atoms bonded together by chemical bonds (H2 or O2)
• Mass number is the total number of protons and neutrons in an atom's nucleus. It is the bigger number.
• Atomic number is the number of protons in an atom of an element. It is the smaller number.
• Protons are positively charged.
• Neutrons are neutrally charged.
• Electrons are negatively charged.
• The mass of one electron is very small compared to that of a proton, so it can be ignored when calculating atomic masses.
• The mass of a single electron is very small compared to that of a proton or neutron.