The Periodic Table

• How is the periodic table arranged?

  By increasing atomic number
• Mendeleev left gaps for the elements he thought hadn't been discovered yet
• Metals form positively charged ions and non-metals from negatively charged ions
• Metals want to lose electrons but non-metals want to gain electrons
• Metals


  -Shiny

  -Sonorous (make a sound when hit)

  -Conduct electricity (due to its free electrons)

  -Malleable

  -Ductile

  -High density

  -Conduct heat
• Noble gases-Group 0
• Noble gases are inert (unreactive) and do not easily form molecules because their atoms have stable arrangements of electrons (full outer shell)
• Noble gases exist as single atoms
• Mendeleev - Helium first discovered in 1895 because it was stable
• As the boiling point increases down group as R.A.M increases
• As the atoms get larger the intermolecular forces get stronger, so they require more energy to overcome
• The density increases down the group
• The halogens - Group 7
• The halogens

  -So reactive

  -Can't exist free in nature

  -Diatomic (in pairs)

  -> e.g, F2,Br2,Cl2
• Why are they so reactive

  -Have 7 e- in the outermost shell

  -Want to gain an electron
• Halogens are non-metals and they all have similar reactions because of the 7 e-
• Fluorine and Chlorine are gases at room temp

  Bromine is a liquid at room temperature

  Iodine is a solid at room temperature
• General Properties

  -Toxic and smelly

  -Crumbly when solid
• Reactivity of group 7 decreases down the group as the outer electrons are further from the nucleus,therefore there is more electron shielding and less attraction between the outer electrons and positive nucleus