Groups 15 to 18: Oxides, Halides and Noble Gases
Groups 15 to 17 show decreasing non-metallic character down each group, while group 18 elements are largely inert with xenon forming fluorides and oxides.
What is Groups 15 to 18: Oxides, Halides and Noble Gases?
Groups 15 to 17 show decreasing non-metallic character down each group, while group 18 elements are largely inert with xenon forming fluorides and oxides.
Key formula / rule: Acidic character of oxides decreases down a group.
Key points
- Compare the acidic character of oxides across and down the p-block.
- Explain the formation of xenon compounds despite noble gas stability.
Common exam trap
Assuming all noble gases are chemically inert.
Definitions
- Term
Groups 15 to 18: Oxides, Halides and Noble Gases
- Meaning
Groups 15 to 17 show decreasing non-metallic character down each group, while group 18 elements are largely inert with xenon forming fluorides and oxides.
- Term
Groups 15 to 18: Oxides, Halides and Noble Gases — explanation
- Meaning
Oxide acidity decreases down a group as metallic character rises, and hydride stability falls as the bond becomes longer and weaker. Xenon compounds exist because its ionisation energy is low enough for fluorine to oxidise it.
Learning objectives
Compare the acidic character of oxides across and down the p-block.
Explain the formation of xenon compounds despite noble gas stability.
Formulae
- Key point
Acidic character of oxides decreases down a group.
- Key point
Hydride thermal stability decreases down groups 15 to 17.
- Key point
Xenon forms fluorides such as XeF2, XeF4 and XeF6.
Prerequisites
CHE-U3-PB-T1-S1-C1
Common mistakes
Assuming all noble gases are chemically inert.
Ranking oxide acidity by molecular size alone.
Keywords
Groups
Oxides
Halides
Noble
Practice preview
Which of the following halogens disproportionates in water to form HX and HXO (or HXO3)?…
hard
Which of the following oxides of Group 15 elements is amphoteric in nature?…
easy
Which of the following halogens has the highest electronegativity?…
easy