Playbook
Elements of Group 16, 17 and 18
48 q - 1.29/paper - 2% HARD, and rising in 2025. Trends, oxoacids, interhalogens and xenon fluorides.
- Questions in the bank
- 48
- q/paper (2024–25 papers)
- 1.29
- Tagged HARD
- 2%
- Subtopics
- 3
Strand: Recall
When you’ll see it
Oxygen, sulphur or ozone; a halogen, interhalogen or oxoacid; a noble gas compound — or a trend down a group.
How this chapter is tested
48 q at 1.29 a paper, 2% HARD — and rising, from 1.00 a paper in 2023-24 to 1.38 in 2025. Group 16 (24 q, never HARD): hydride trends (thermal stability falls and acidity rises from H₂O to H₂Te), allotropes of sulphur, ozone, and oleum.
Group 17 (21 q): oxidising power (F₂ strongest), the oxoacids and their oxidation states, and interhalogens. Group 18 (3 q): xenon fluorides and their shapes.
The sub-skills
The distinct skills inside the chapter, in the order to learn them.
Hydride trends
H₂O → H₂Te: stability falls, acidity rises, boiling point lowest at H₂S (water is high from hydrogen bonding).
Oxoacids
Cl in HClO +1, HClO₂ +3, HClO₃ +5, HClO₄ +7; acid strength rises with oxidation state.
Xenon compounds
XeF₂ linear, XeF₄ square planar, XeF₆ distorted octahedral.
Traps to expect
Distractor shapes this chapter reuses. The Traps page covers the patterns that cut across chapters.
Water's boiling point
The boiling-point trend reverses at water because of hydrogen bonding; H₂S, not H₂O, is lowest.
Oleum's formula
Oleum is H₂S₂O₇ (pyrosulphuric acid), not H₂SO₄.
Learn it before you drill it
This chapter has full teaching notes — foundations, worked examples, self-checks and a per-subtopic mastery checkpoint. Read the notes once, then drill subtopic by subtopic below.
Elements of Group 16, 17 and 18 notesDrill every elements of group 16, 17 and 18 question
48 questions from the bank, scoped to 3 bundled subtopics.
Drill one subtopic at a time
The 3 subtopics this playbook covers, in catalog order.
Related playbooks
Often paired with this one — the technique, the trap or the taxonomy overlaps. Drill these next.