chemistry

• Elements are classified into metals (on the left side) and non-metals (on the right side).
• The periodic table is arranged by increasing atomic number, with elements having similar properties grouped together.
• All substances are made up of atoms, which are made up of protons, neutrons and electrons.
• Atoms have a radius of about 0.1 nanometres.
• The nucleus is in the middle of the atom, it contains the protons and neutrons.
• The nucleus has a positive charge because of the protons.
• The electrons move around the nucleus in electron shells.
• Electrons are negatively charged and tiny but they cover alot of space.
• Number of protons equals number of electrons.
• Atoms are neutral because they have the same number of protons and electrons.
• In an ion, the number of protons doesn't equal the number of electrons.
• The atomic number tells you how many protons they are.
• The mass number tells you the total number of protons and neutrons in the atom.
• Number of neutrons = mass number - atomic number
• An element is a substance that is made up of only one kind of atom.
• A compound is a pure substance made from more than one type of element chemically bonded together.
• A mixture is a combination of two or more substances in any proportions.
• Carbon dioxide = CO2
• Ammonia = NH₃
• Water = H₂O
• Sodium Chloride = NaCl
• Carbon monoxide = CO
• Hydrochloric acid = HCl
• Calcium chloride = CaCl₂
• Sodium carbonate = Na₂CO₃
• Sulfuric acid = H₂SO₄
• Evaporation is a process by which an element or compound transitions from a liquid to a gas.
• Crystallisation is the process of formation of solid crystals from solution, where the solvent is evaporated.
• Filtration is used to separate liquids from insoluble solids through the use of a filter.
• Chromatography is used for separating a mixture of chemical substances into its components.
• Neutrons have a neutral charge.
• In 1932, James Chadwick discovered the neutron which led to a revision of the cloud model of the atom.
• The plum pudding model was developed by J J Thomson in 1897. He concluded that the electrons were embedded in positive charge spheres called plum puddings.
• In the plum pudding model, there is a positive sphere with negative charge randomly placed within the sphere. There is no empty space. In the nuclear model, there is a central positive, tiny nucleus, with mostly empty space and lots of negative charges a long way from the nucleus.
• The relative mass of a proton and neutron is 1.
• The relative mass of an electron is 0.0005
• Distillation is used to separate mixtures which contain liquids.
• Isotopes are forms of an element that have the same number of protons but a different number of neutrons.
• Electrons fill energy levels in an atom by occupying the lowest available energy level first. This is the shell nearest the nucleus. When this shell is full, the electrons occupy the next energy level.
• The first shell in an atom always consists of only two electrons and the rest of the shells onwards are filled with up to eight electrons.