Chem Yr9

• The periodic table is organised by atomic number
• Atomic mass = protons + neutrons - electrons
• Isotopes are atoms with the same amount of protons but different amounts of neutrons.
• A molecule is two or more atoms joined together chemically
• A compound is made up of two or more elements chemically bonded together
• A compound is made up of two or more elements chemically bonded together.
• Elements can be represented as symbols or names.
• An element is made up of only one type of atom
• Compounds are elements that have been combined to form new substances
• Mixtures contain two or more elements/compounds mixed together, not bonded together
• Elements can exist as pure metals, non-metals or gases
• The periodic table shows how elements are arranged based on their atomic structure, properties, and reactions.
• Elements that have similar chemical properties are grouped together in columns called groups.
• Groups are numbered from 1 to 8 (I - VIII) with the most reactive at the top.
• Non-metals do not conduct electricity well and are usually brittle solids at room temperature.
• Gas atoms are far apart from each other so they move quickly and randomly
• Non-metals are dull, brittle, poor conductors of heat and electricity, do not react with water and are usually coloured
• Metals are shiny, hard, good conductors of heat and electricity, malleable (can be hammered into shape) and ductile (can be drawn out into wires)
• Non-metals are found on the right side of the periodic table
• Metals are found on the left side of the periodic table
• Ions are charged particles formed when electrons are gained or lost by atoms.
• The periodic table organises all the known elements into groups based on their properties
• Non-metals are located below Group 2 and include all noble gases.
• Metals are good conductors of heat and electricity, malleable, ductile, shiny, and form positive ions when they react.
• Liquid molecules are close together but still moving around rapidly
• Solid particles are packed tightly together and vibrate about fixed positions
• Melting point is when a solid turns into liquid
• Electron shells fill up starting with one electron in the first shell, then two in the second, eight in the third, etc.
• The noble gases have very low boiling points because their molecules are small and weakly attracted to one another
• Oxygen makes up most of our atmosphere and is essential for life as we know it
• Carbon is used to make plastics, polymers, fuels and fertilisers
• Noble gases are unreactive as they already have full outer shells
• Group 1 metals have one valence electron that is easily given away to form positive ions with a charge of +1.
• Group 0 non-metals share their outer shell electrons to form molecules.
• Non-metals do not have these characteristics and can be solid, liquid, gas, or plasma at room temperature.
• Group 1 metals are called alkali metals because they react with water to produce hydrogen gas and an alkaline solution.
• Elements that exist as molecules (compounds) at room temperature are non-metals.
• Gas molecules have lots of space between them and move very quickly
• Melting point is the temperature at which a solid turns to liquid
• Solids have strong forces of attraction holding the particles tightly packed together