Chemistry 2.2

• Atom


  Made up of protons, electrons and neutrons
• Nucleus of an atom

  • Contains majority of the mass
  • Contains positively charged protons
  • Contains neutrons
• Electrons


  • Have negative charge to balance out positive charge of protons
  • Surround the nucleus
• Atom has an overall charge of 0
• Steps of drawing an atom

  1. Determine atomic number (number of protons)

  2. Determine atomic mass number (total number of protons and neutrons)

  3. Determine number of shells based on periodic table

  4. Number of electrons equal to number of protons, filling from inner shell first
• Isotopes


  Different types of atoms of the same element with different numbers of neutrons
• Chlorine has two isotopes, Cl-35 and Cl-37
• Metals


  • Found on left and middle of periodic table
  • Have few electrons in outer shell
• Properties of metals


  • High melting and boiling points
  • Good conductors of heat and electricity
  • Solid/dense/heavy
  • Can be stretched into wires (ductile)
  • Can be bent into shape (malleable)
  • Shiny
  • Sonorous (make ringing sounds)
• Non-metals


  • Found on right of periodic table
  • Have many electrons in outer shell
• Properties of non-metals


  • Lower boiling and melting points
  • Not good conductors of heat or electricity
  • Brittle (breaks easily)
  • Dull appearances
• Metalloids (semi-metals)


  • Found in middle right of periodic table
  • Have properties/resemblance to both metals and non-metals
  • Semi-conductors
• Elements try to achieve full outer shell (group 0) by losing or gaining electrons
• Alkali metals (Group 1)

  • Have 1 electron on outer shell that is easily lost
  • Reactive, float on water, melt in water, can burst into flames
• Halogens (Group 7)


  • Have 7 electrons on outer shell that are easily gained
  • Colourful vapours, toxic, reactivity decreases down group
• More reactive element in a compound will displace less reactive element