Chemistry (C1)

• the periodic table is organised by atomic number
• isotopes are atoms with the same number of protons but different numbers of neutrons
• a molecule is two or more atoms chemically bonded together
• an ionic compound has positive and negative ions held together by electrostatic forces
• covalent compounds have shared pairs of electrons between non-metal atoms
• Electron arrangement in Shell 4=2e is a characteristic of L6: Electron arrangement in Shell 4=2e is a characteristic of L6:
• The structure of ions is a topic of L7: Structure of ions is a topic of L7:
• Chromatography involves separating solids, liquids, and gases based on their physical properties.
• A mixture is a 1+ substance that is not chemically bounded.
• Formation refers to a mixture designed by humans for a specific purpose.
• Pure is a substance made of only one element or compound.
• Compounds and mixtures can be formed through a chemical reaction that has a fixed composition and involves chemical bonds between atoms of different elements.
• Elements can be separated easily (by physical means) and have no fixed compositions.
• There are no chemical bonds between atoms of different types of elements.
• Filtration, combustion, evaporation, solubility, oxidation, displacement, and neutralisation are methods used in the separation of compounds and mixtures.
• The group number of an element tells you how many electrons there are in the outer shell.
• The period number tells you how many electron-containing energy shell the element has.
• Atoms have both + and - electrons, making them neutral.
• Ions have more electrons, changing them to be + and - charged.
• + ions are called cations.
• - ions are called anions.
• The electron structure of Li+ is 3, 4, 2, 2.
• The electron structure of F- is 9, 10, 10, 2, 8.
• The electron structure of Mg2+ is 12, 12, 10, 2, 8.
• Electrons can be lost or gained.
• Relative fraction (RF) is the distance travelled by a chemical or solvent.
• John Dalton discovered in 1803 that atoms were spheres that could be broken down to the same proportion, regardless of the element.
• John Dalton also stated that atoms could never be created or destroyed.
• In 1897, JJ Thompson proposed the plum pudding model, which consists of uniformly sized spheres that are positive charge filled with negative charge electrons.
• Rutherford's model in 1911 consists of large empty space where most of the mass is located at the centre, which is the nucleus.
• Niels Bohr discovered in 1915 that electrons orbit the nucleus at a fixed energy and distance, and are able to jump between but not exist in space, which he referred to as shells.
• Chadwick found in 1932 that neutrons lived with protons in the nucleus.