The Periodic Table

• the periodic table is arranged by increasing atomic number
• Mendeleev left gaps for the elements he thought hadn't been discovered yet
• Metals- positively charged ions (lose e-)

  Non-metals- negatively charged ions(gain e-)
• Properties of metals

  • shiny
  • sonorous
  • ductile
  • malleable
  • high density
  • conduct electricity and heat (due to its free electrons)
• Why are noble gases unreactive?

  this is because they have full outer shells
• noble gases are inert and don't easily form molecules because their atoms have stable arrangements of electrons
• noble gases exist as single atoms
• the first discovered element on the periodic table was helium in 1895 because it was stable
• What happens to the reactivity of elements down group 1?

  the reactivity of group 1 elements increases down group 1 because the atoms get larger and the outer electron gets further away from the nucleus and there is less attraction
• Why are the halogens so reactive?

  they have 7 electrons in their outermost shell and they want to gain an electron
• Why does the reactivity of group 7 decrease down the group?


  they increase in electron shells; so the atoms are larger as you go down the group and the atomic mass increases