Coaching Centre
Elements, compounds and mixtures review
A summary of the whole Elements, Compounds and Mixtures chapter, key words, and a mixed test covering atoms, the periodic table, properties, metals and non-metals, compounds and formulas, mixtures and the history and modern uses of materials.
Use this page to check the whole chapter. Read the summary, make sure you can explain every key word, then do the test without looking back.
Chapter summary
| Topic | What you need to know |
|---|---|
| 4A Atoms | Particle model / kinetic theory. Nucleus: protons (+) and neutrons (0); electrons (−) in shells. Atomic number = protons (decides the element). Mass number = protons + neutrons. Isotopes and ions. Thomson (electron), Rutherford's gold foil (nucleus), Chadwick (neutron), LHC. |
| 4B Elements and the periodic table | Element = one kind of atom. Symbols (capital + lower case; Latin names Au, Ag, Fe, Cu, Pb, Na, K, Hg) are used worldwide. Mendeleev's table and predictions. Groups (columns), periods (rows). Metals left, non-metals right, metalloids between. 118 elements; newest named 2016. |
| 4C Properties | Physical: state, melting/boiling point, lustre, density, hardness, conductivity, malleability, ductility, viscosity. Chemical: flammability, reactivity, corrosion (rust, passive layers, patina), toxicity (depends on dose). |
| 4D Metals, non-metals and allotropes | Metals: lattice in a sea of electrons, so conductive, malleable, ductile, shiny. Non-metals: electrons held in bonds; brittle insulators; monatomic (He) or diatomic (O₂, N₂). Allotropes: diamond, graphite, graphene; O₂ and O₃. Uses linked to properties. |
| 4E Compounds | Two or more elements chemically bonded in a fixed ratio; new properties; broken down only by chemical reactions (decomposition). Formulas: capitals = elements, subscripts = number of atoms. Molecules (H₂O, CO₂, CH₄) and lattices (NaCl). Polymers. |
| 4F Mixtures | Not bonded; variable proportions; parts keep their properties; separated physically. Homogeneous (air, seawater, alloys) vs heterogeneous (sand, soil). Alloys: steel, stainless steel, bronze, brass. Particle diagrams. |
| 4G Materials through history | First Nations Australians: ground-edge axes (44 000+ years), heat-treated stone, resin adhesives, ochre, fibres, trade. Stone, Copper, Bronze, Iron Ages. Smelting with charcoal. Bronze = copper + tin; steel = iron + carbon. |
| 4H Modern world | Electrolysis (copper, aluminium from bauxite), electroplating. Steel and sulfuric acid. Elements in a phone. Critical minerals, non-renewable ores, recycling and e-waste. |
Putting it together
Everything in this chapter comes back to one idea: a substance's properties come from its particles and how they are arranged. Copper wires bend and conduct because of a sea of free electrons. Diamond is hard and graphite slippery because the same carbon atoms are joined differently. Salt is safe to eat although sodium and chlorine are dangerous, because bonding makes a new substance. Air can be separated into its gases because they are only mixed. And for 3 million years, people have been making use of these properties, from shaping greenstone axes to building smartphones.
Key words
allotrope · alloy · atom · atomic number · bronze · chemical formula · chemical property · compound · conductivity · corrosion · decomposition · diatomic · ductile · electrolysis · electron · element · flammability · group · heterogeneous · homogeneous · ion · isotope · kinetic theory · lattice · lustre · malleable · mass number · metal · metalloid · mixture · molecule · monatomic · neutron · non-metal · nucleus · ore · period · periodic table · physical property · polymer · proton · smelting · steel · subscript · toxicity · viscosity
Test yourself
An atom has 17 protons, 18 neutrons and 17 electrons. Which element is it?
17 protons = atomic number 17 = chlorine.
The symbol Pb stands for
From the Latin plumbum.
Which is a physical property?
Testing conductivity doesn't change the substance.
Metals are malleable because
The layers move without breaking apart.
How many atoms are in one molecule of glucose, C6H12O6?
6 + 12 + 6 = 24.
Which is a homogeneous mixture?
Pure water is a compound, not a mixture.
Diamond and graphite are both pure carbon, but diamond is much harder because
Graphite's sheets slide apart.
Which pair of substances is correctly matched?
Bronze is copper + tin; steel is iron + carbon.
Iron filings and sulfur powder stirred together form
They aren't bonded until heated.
Aluminium only became cheap after 1886 because
The Hall–Héroult process.
Label the atom.
Classify each.
The number of protons in an atom is its . A column of the periodic table is a . Different forms of the same element are . A pure substance made of two or more elements bonded together is a . Extracting a metal from its ore with heat is .
Water (H2O), oxygen (O2) and air are all made of molecules. Classify each as an element, compound or mixture. For each, describe what its particles would look like in a particle diagram and justify your classification.
Water is a compound. In a particle diagram every particle would be the same: a molecule made of one oxygen atom bonded to two hydrogen atoms. It contains two different elements chemically bonded in a fixed 2 : 1 ratio.
Oxygen gas is an element. Every particle is the same: a molecule of two oxygen atoms bonded together. It is a molecule, but it is not a compound, because it contains only one kind of atom.
Air is a mixture. A particle diagram would show several different kinds of particle jumbled together: nitrogen molecules (N₂), oxygen molecules (O₂), single argon atoms, and a few carbon dioxide and water molecules. They are not bonded to each other, each keeps its own properties, and the proportions can vary (for example, the amount of water vapour changes with the weather).