Revision Tips: Periodic Table

This is NOT a substitute for learning, just a few little hints and tips.

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

Remember:

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
  • Monatomic
  • 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, 1ions 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.


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Hints and Tips: Getting it Right in Practical Papers

READ ALL the question first. You have plenty of time. Imagine the apparatus in front of you.

Measurement on-site. For lengths, make sure you have a good quality ruler, able to measure accurately to 1mm. You are usually provided with pretty much everything you might need and, if you are, it’s important to use it all. As an example, if you’re measuring the diameter of a marble and they give you six, plus a ruler and two set squares, this is the way to do it.

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Decide where a measurement is to be taken (top/middle/bottom) For example, the length of a pendulum is measured from the support to the middle of the lead weight.

First create a table with headers, then write the measurements down to the nearest unit on the measuring instrument (such as 1 degree or 1mm)

The question often asks you to process the measurement in some way (work out an area or volume/divide by a number of oscillations/ find the sine of an angle/find a volume.) Do the algebra or rearrange first. Then put in the numbers. Quote your answer to the number of decimal places in the question and don’t forget units.

There is often data where you have to fill in the units and there will always be a graph to plot (e.g, a cooling curve) Use sensible and easy-to-plot scales for the graphs and remember that the axes have units. Draw the LOBF through as many data points as possible. Look down the points to see whether it’s a straight line or not. If it is, use a ruler. If not, draw freehand a smooth curve and, if you’re using error bars the line MUST go through them all, both vertical and horizotal Use a sharp HB pencil

The graph tells you something. Think about what the data is telling you – they will either ask you to work out a gradient or an area. Gradients – big is beautiful and keep it simple – look out for division by easy numbers. Both gradient and area under will have units.

You are sometimes asked to read meters. Be careful about accuracy and sensitivity. We used to use these big demonstration meters in school but now mostly they are all digital. You should know how to read both, however.

Precautions to ensure accuracy. When reading meters, volumes from measuring cylinders, lengths and so on, avoid parallax errors. Repeat measurements and average as time allows (3 is good) and zero all meters are the usual ones to write down when asked to comment.