Chemistry unit 2 These revision cards give an overview of the entire Chemistry unit. 2.0 / 5 based on 2 ratings ? ChemistryNanoscienceGCSEAll boards Created by: Rachel HallCreated on: 24-04-10 12:28 Atoms Atoms consist of electrons surrounding a nucleus that contains protons and neutrons. The number of electrons in the outermost shell has a direct link to the group number that the element is found in. Protons have a mass number of 1, and a charge of +1. Neutrons have a mass number of 1, and a charge of 0. Electrons have an extremely small mass number, and a charge of -1. The mass number is the TOP NUMBER. The atomic number is the BOTTOM NUMBER. Elements consist of one type of atom only. 1 of 2 Chemical Bonding. Ions are electrically charged particles formed when atoms lose or gain electrons. Metal atoms lose electrons to become postively charged ions. Non-metal atoms gain electrons to become negatively charged ions. The strong forces of attraction between oppositely charged ions are called ionic bonds. These strong forces therefore require a lot of energy to be broken, and consequently ionic bonds have high melting and boiling points. SHARING ELECTRONS - covalent bonding. TRANSFERRING ELECTRONS - ionic bonding. 2 of 2
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