Elements, Compounds and Symbols

50 lessons, pages 221–270.

  1. Elements: The Simplest Substances — Substances that cannot be broken down chemically
  2. Atoms and Elements — Every element is made of one kind of atom
  3. How Many Elements Are There? — 118 known elements and how new ones are confirmed
  4. Natural and Synthetic Elements — About 90 elements in nature and the rest made in laboratories
  5. Why Chemists Use Symbols — A shared international shorthand for elements
  6. From Dalton's Circles to Berzelius's Letters — How chemical symbols developed historically
  7. One-Letter Element Symbols — H, C, N, O and other single capital letters
  8. Two-Letter Symbols and Capital Letters — Why Co and CO mean different things
  9. Symbols from Latin Names — Na, K, Fe, Cu, Ag, Au, Pb and Sn
  10. Elements Named After Places, People and Properties — The stories behind element names
  11. Metals, Non-metals and Metalloids — Classifying elements by their properties
  12. Elements at Room Temperature — Which elements are solids, liquids and gases
  13. A First Look at the Periodic Table — Arranging elements by atomic number
  14. Groups and Periods: Locating an Element — Reading columns and rows of the periodic table
  15. Elements That Exist as Molecules — Diatomic elements such as H₂, O₂, N₂ and Cl₂
  16. Allotropes: One Element, Different Forms — Diamond, graphite and the forms of oxygen
  17. What Is a Compound? — Two or more elements chemically combined
  18. Compounds Versus Mixtures — Fixed composition and chemical bonding versus physical mixing
  19. Compounds Have New Properties — Sodium chloride compared with sodium and chlorine
  20. The Law of Constant Composition — A compound always has the same elements in the same mass ratio
  21. Forming Compounds from Elements — Synthesis reactions and energy changes
  22. Breaking Compounds Down — Decomposition by heat and electricity
  23. Molecules of Elements and Molecules of Compounds — Particle diagrams for elements, compounds and mixtures
  24. Ionic and Molecular Compounds: A First Look — Metal–non-metal versus non-metal–non-metal compounds
  25. Chemical Formulae: What They Tell Us — Which elements are present and in what ratio
  26. Subscripts in Chemical Formulae — Reading the small numbers in H₂O and CO₂
  27. Brackets in Chemical Formulae — Groups of atoms such as in Ca(OH)₂
  28. Counting Atoms in a Formula — Systematic atom counting including brackets
  29. Coefficients Versus Subscripts — 2H₂O compared with H₂O₂
  30. Molecular and Empirical Formulae: An Introduction — Actual numbers of atoms versus simplest ratio
  31. Naming Binary Compounds — Metal first and the -ide ending
  32. Names Ending in -ate and -ite — Compounds containing oxygen in a polyatomic group
  33. Prefixes in Compound Names — Mono-, di-, tri- and tetra- in molecular compounds
  34. Common Names of Familiar Compounds — Water, ammonia, methane, salt and chalk
  35. Valency: The Combining Power of an Element — How many bonds or hydrogen atoms an atom combines with
  36. Finding Valency from Hydrogen Compounds — HCl, H₂O, NH₃ and CH₄ as a valency ladder
  37. Valencies of Common Elements — Patterns linked to position in the periodic table
  38. Variable Valency and Roman Numerals — Iron(II), iron(III), copper(I) and copper(II)
  39. Polyatomic Ions and Their Valencies — Hydroxide, nitrate, sulfate, carbonate and ammonium
  40. Writing Formulae by Crossing Valencies — The swap-and-drop method for binary compounds
  41. Writing Formulae with Polyatomic Ions — When and why brackets are needed
  42. Simplifying and Checking Formulae — Lowest ratios and balancing charges
  43. From Name to Formula: Guided Practice — Converting compound names into formulae
  44. From Formula to Name: Guided Practice — Converting formulae into systematic names
  45. Relative Atomic Mass: A First Look — Comparing atom masses on the carbon-12 scale
  46. Relative Formula Mass — Adding relative atomic masses from a formula
  47. Percentage by Mass of an Element in a Compound — Using formula masses to find composition
  48. Common Errors in Writing Formulae and Symbols — Capitalisation, brackets, charges and ratios
  49. Elements and Compounds in Everyday Life — From the air we breathe to the materials we use
  50. Elements, Compounds and Symbols: Unit Review — Bringing together symbols, compounds, formulae and valency