Atoms, Elements and Compounds

Cards (12)

  • All substances are made of atoms
  • An atom is the smallest part of an element that can exist
  • An element is a substance that contains only one sort of atom (There are about 100 different elements)
  • Elements are displayed in the periodic table
  • The atoms of each element are represented by a different chemical symbol (e.g. sodium = Na)
  • Most substances are compounds
  • Compounds contain two or more elements - they are chemically combined in fixed proportions
  • Compounds are represented by a chemical formula
  • A chemical formula is a combination of numbers and chemical symbols
  • Why do scientists use chemical formulae?
    To show the different elements in a compound - To show how many atoms of each element one molecule of the compound contains
  • Water contains 2 hydrogen (H) atoms and 1 oxygen (O) atom , so its chemical formula would be H₂O
  • Sulfuric acid contains 2 hydrogen (H) atoms , 1 sulfur (S) atom, and 4 oxygen (O) atoms, so its chemical formula would be H₂SO₄