atomic structure and periodic table

• Element

  All of the atoms are the same
• Elements

  • Magnesium
  • Sulfur
• Element symbol

  Starts with a capital letter
• Compound

  Contains two or more different elements chemically combined in fixed proportions
• Compounds usually have totally different properties to the elements they are made from</b>
• Mixture

  Contains different elements or compounds, but they are not chemically combined
• Separation techniques for mixtures

  • Filtration
  • Distillation
  • Crystallization
  • Chromatography
• Molecule

  Any elements chemically combined, even if they are the same element
• Molecules

  • Methane
  • Water
  • Ammonia
  • Chlorine
  • Oxygen
• Molecules that are not compounds contain the same element chemically combined
• Chemical formula

  Tells us the elements in a molecule and the numbers of atoms of each element
• In a specific compound, the number of atoms of each element is fixed</b>
• Chemical formula

  • Shows the symbol for each element
  • Shows the number of atoms of each element
• Interpreting a chemical formula

  1. Identify the elements

  2. Determine the number of atoms of each element
• Brackets in a chemical formula indicate that the numbers inside the brackets apply to everything inside
• Changing the number of atoms of an element in a compound results in a different compound