The Periodic Table is a core part of IB Chemistry. Revise the key concepts and common mistakes below, then lock them in with the free games.
Key concepts
Periodic lawProperties repeat by atomic number
Atomic radiusHalf nucleus-nucleus distance
Ionisation energyEnergy to remove 1 e⁻
ElectronegativityAbility to attract bonding e⁻
ShieldingInner shells reduce nuclear pull
Pauling scaleF = 4.0, Cs = 0.7
Basic oxideReacts with acid (metal oxide)
Acidic oxideReacts with base (non-metal)
AmphotericReacts with both (Al₂O₃)
Ionic oxideMetal+oxide ion (high mp)
Covalent oxideMolecular or giant covalent
HydrolysisReaction with water
Transition metalForms ions with incomplete d sub-shell
Variable OSMultiple oxidation states (Fe²⁺, Fe³⁺)
Common mistakes to avoid
Questions where students often pick the tempting wrong answer — make sure you know the right one:
If a complex ion has a coordination number of 4, what shape does it have?✗ A coordination number of 4 always means tetrahedral, because that gives the maximum bond-angle separation. ✓ It can be either tetrahedral OR square planar — the shape depends on the metal and ligands (e.g. [Pt(NH3)4]2+ is square planar; [CuCl4]2- is tetrahedral).
Why does the colour of a transition metal complex change when ligands are exchanged?✗ The colour changes because the metal ion itself changes oxidation state. ✓ Different ligands cause different amounts of d-orbital splitting, so different wavelengths of light are absorbed.
What does the M+ peak in a mass spectrum represent?✗ The M+ peak shows the mass of the largest fragment after the molecule breaks apart. ✓ The molecular ion — formed when a single electron is removed from the whole molecule, giving the relative molecular mass.
Why is the hydration enthalpy of a small, highly charged ion very exothermic?✗ Hydration enthalpy only depends on the size of the ion, not its charge. ✓ Small/highly charged ions form strong ion-dipole attractions with water molecules, releasing a large amount of energy.
Why is the 4s orbital filled before the 3d orbital?✗ Because the 4s shell is closer to the nucleus than the 3d shell. ✓ Because the 4s orbital has a lower energy than 3d when both are empty, so electrons fill it first.
Practise The Periodic Table — free games
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