Groups go DOWN (similar properties), periods go ACROSS (properties change from metal to non-metal)
You should be able to draw an electron configuration up to a proton number of about 20
Magnesium 2,8,2, Group 2 period 2,
Calcium 2,8,8,2, Group 2 period 3
Shell 1 2 electrons
Shell 2 8 electrons
Shell 3 8 electrons
Shell 4 18 electrons
Group 1 metals
- From Li to Fr reactivity increases down the group 1 electron in outermost shell. Form 1+ ions
- Form ionic compounds, white solids that dissolve in water to form colourless solutions
- Highly reactive with water, oxygen and the halogens, kept under paraffin
- Atoms get bigger down the group so electron further away from nucleus
- Good conductors of heat and electricity
- Often very soft can be cut with a knife
- Float on water – low density
- Low mp and bp
(Group II metals (Mg, Ca) have 2 electrons to give away so in general are less reactive than their corresponding group I metal)
Halogens Group VII (7)
- Ionic bonding with metals e.g NaCl, 1– ions formed
- Covalent molecular bonding, diatomic e.g Br2 so low mp and bp increasing down group
- 1 vacancy in outermost shell
- Reactivity decreases down the group because vacancy further away from the nucleus – more difficult to fill it. Cl displaces Br displaces I
- React with metals to form metal salts Example?
- Do I remember the test for a chloride? If not, look it up now.
- Chlorine gas will displace bromine from sodium bromide (Cl more reactive than Br) – green gas turns to brown gas
Noble Gases Group 0 or VIII (8)
- Don’t do much at all. No free electrons in outermost shells
- All monatomic
- Uses: He balloons (very light), Ar in filament lamps (because very unreactive – prevents contamination of the filament), Ne in signs (glows bright green),Xe in flash photography (stroboscopes).
- He/Ne used in lasers (glows red)
Transition Metals – identify where they are in the PT
- frequently colourful compounds (salts) – used in stained glass windows
- high mp and bp.
- high density – none float like Na on water
- hard, tough and strong, malleable and ductile
- good conductors of heat and electricity
- crystalline, hence shiny.
- often alloyed to get the best of both worlds (Ti is alloyed for lightness, strength and corrosion resistance), bronze = Cu alloyed with Sn (tin), harder than Cu alone.
- mainly vary in their inner electrons so often quite similar chemically.
- uses for iron (steelmaking), copper (electrical wiring and water pipes) and zinc (anti-corrosion coatings)
- catalysts – metals like palladium, gold and platinum used often to increase the surface area for reactions to occur. Iron catalyses the Haber Process for ammonia manufacture.
- A few to remember – potassium permanganate (Mn in oxidation state VII) KMnO4 is purple, potassium dichromate (the Cr is in oxidation state VI) K2Cr2O7 is orange. Both are strong oxidising agents and on reduction their colours change. permanganate becomes colourless, dichromate turns from orange to green.