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O-Level Patterns in the Periodic Table
periodic trends, group behaviour, transition elements and the reactivity series
What the syllabus expects
- Describe the Periodic Table as elements laid out in order of increasing proton (atomic) number.
- Explain how an element's place in the Periodic Table relates to its proton number and electronic configuration.
- Describe how, for the first twenty elements, the number of outer (valence) electrons relates to the charge of an ion.
- Explain why elements in the same group behave similarly by reference to their electronic configurations.
- Describe how character changes from metallic to non-metallic moving from left to right across a period.
- Describe how the number of outer (valence) electrons relates to whether an element is metallic or non-metallic.
- Use the Periodic Table to predict the properties of Group 1 and Group 17 elements.
- Describe the Group 1 alkali metals lithium, sodium and potassium as fairly soft, low-density metals that show trends in melting point and in how they react with water.
- Describe the Group 17 halogens chlorine, bromine and iodine as diatomic non-metals showing trends in colour and state and in how they displace one another from solutions containing other halide ions.
- Describe the Group 18 noble gases as unreactive single-atom elements valued for providing an inert environment, such as helium in balloons, argon and neon in light bulbs, and argon in steelmaking.
- Account for the noble gases' inertness in terms of their electronic configurations.
- Describe a typical transition element as a dense, high-melting metal that shows variable oxidation states and forms coloured compounds.
- State that transition elements and/or their compounds often function as catalysts.
- Rank calcium, copper, (hydrogen), iron, lead, magnesium, potassium, silver, sodium and zinc by reactivity, using how the metals react with water, steam and dilute hydrochloric acid, and whether carbon and/or hydrogen can reduce their oxides.
- Explain the reactivity series as reflecting how readily a metal forms its positive ion, shown by its reactions with the aqueous ions and with the oxides of the other listed metals.
- From a supplied set of experimental findings, work out the order of reactivity.
- Describe what heating the listed metals' carbonates does and relate their thermal stability to the reactivity series.
- Explain, by linking each element's position in the reactivity series, how readily metals can be won from their ores.
- State that iron rusts only when both oxygen and water are present, and that rusting can be prevented with a barrier such as painting, greasing, plastic coating or galvanising.
- Explain how iron gains sacrificial protection when a more reactive metal fixed to it corrodes first owing to its higher place in the reactivity series, as when magnesium is attached to underwater pipes.
How it's examined
Questions on this topic most often ask you to explain, identify, show. About 11% of the past-paper style questions in Rae's bank for this subject sit in this topic.
Worked examples
Example 1 (2 marks)
Give the full electronic configuration of a chromium atom and of a nickel atom. Cr: 1s2 ... Ni: 1s2 ...
Show the worked answer
Chromium (Z = 24) shows the well-known exception where one 4s electron promotes to 3d to give a more stable half-filled 3d5 arrangement: Cr: 1s2 2s2 2p6 3s2 3p6 3d5 4s1 Nickel (Z = 28) follows the normal order: Ni: 1s2 2s2 2p6 3s2 3p6 3d8 4s2
Example 2 (2 marks)
Give two typical properties of transition metals that set them apart from a Group 2 metal such as magnesium.
Show the worked answer
Transition metals show features that Group 2 metals like magnesium do not: they exhibit variable oxidation states, they form coloured compounds/ions, and they (and their compounds) often act as catalysts. Any two of these are typical distinguishing properties.
Example 3 (2 marks)
OR. This question concerns transition metals and the ions they form. Like a Group 2 metal such as magnesium, transition metals melt only at high temperatures. Explain why transition metals have such high melting points.
Show the worked answer
Transition metals have strong metallic bonding: there is a strong electrostatic attraction between the positive metal ions and the sea of delocalised electrons. A large amount of energy is needed to overcome these strong forces of attraction, so the metals melt only at high temperatures.
More worked questions on this topic
- Certain car parts are made from an aluminium and silicon alloy. Silicon is obtained from the si (2 marks)
- A section of the Periodic Table is shown, with only these elements labelled: H (Period 1); Ne i (5 marks)
More O-Level Pure Chemistry topics
Experimental Chemistry · The Particulate Nature of Matter · Chemical Bonding and Structure · Chemical Calculations · Acid-Base Chemistry · Qualitative Analysis · all of O-Level Pure Chemistry