Inorganic Chemistry: s-, p- and d-Block Elements and Their Compounds
Inorganic Chemistry: s-, p- and d-Block Elements asks for group trends and characteristic reactions of the main-group metals and non-metals, plus the typical behaviour of transition metals and their compounds.
s-Block
Reactivity with water increases down group 1 (K ignites, Li fizzes slowly). Hydroxide basicity increases down the group; Be(OH)₂ is amphoteric. Flame colours: Li crimson, Na yellow, K lilac, Ca brick-red, Ba apple-green. Lithium shows a diagonal relationship with magnesium.
p-Block
The inert-pair effect stabilises lower oxidation states down a group, so Tl(I) and Pb(II) are the stable ions. Oxide acidity increases across a period: Na₂O basic, Al₂O₃ amphoteric, SO₃ acidic. Halogen oxidising power falls from F₂ to I₂; Cl₂ disproportionates in cold dilute NaOH to Cl⁻ and ClO⁻.
d-Block
Variable oxidation states (Mn from +2 to +7), coloured ions, complex formation, catalytic activity and paramagnetism from unpaired d electrons.
Worked example
Mn²⁺ is pale pink and nearly colourless, while MnO₄⁻ is intensely purple. Mn²⁺ is d⁵ high-spin: every d orbital holds one electron, so any d–d transition must flip a spin, which is forbidden and therefore very weak. In permanganate the colour arises from ligand-to-metal charge transfer, an allowed transition with a large molar absorptivity.
Traps
- Sc³⁺ and Ti⁴⁺ are d⁰ and colourless - not every transition-metal ion is coloured.
- Cr(OH)₃ and Al(OH)₃ dissolve in excess NaOH; Fe(OH)₃ does not.
- Explaining the colour of MnO₄⁻ as a d–d transition.