GCSE · Chemistry · AQA · Spec 8462
Proportions of gases in today's atmosphere
You breathe it all day. So what is air mostly made of? Most people say oxygen. Hold on to your answer: the first thing on this page tests it.
Today's atmosphere · Big share or small?
Sort the gases of the air
Pick a gas, then choose the share of today's air it makes up.
Still to sort
About four-fifths of the air (0)
The biggest share by far
About one-fifth of the air (0)
The second big share
A small proportion (0)
Everything that isn't one of the two big shares
Where the line is: Oxygen's one-fifth may sound small, but it's one of the two big shares. 'A small proportion' is for the gases left over once nitrogen and oxygen are counted.
Five names you'll meet in any question about the air. Where does each one belong?
Predict, then check
200 million years is an enormous stretch of time. Go with your gut before you look.
Rewind 200 million years. How do the proportions of the gases in the air back then compare with the proportions today?
WHAT YOU'VE LEARNED
A quick recap of today's lesson.
Two gases take up almost all of it. Make your guess first, then see where their real shares sit.
What you need to know
- Nitrogen makes up about four-fifths (approximately 80%) of today's atmosphere.
- Oxygen makes up about one-fifth (approximately 20%) of today's atmosphere.
- Other gases, including carbon dioxide, water vapour and noble gases, make up small proportions.
- The proportions of the gases have been much the same as today's for 200 million years.
The big picture
Today's atmosphere is about four-fifths (approximately 80%) nitrogen and about one-fifth (approximately 20%) oxygen. The rest is small proportions of various other gases, including carbon dioxide, water vapour and noble gases. For 200 million years, these proportions have been much the same as they are today.
Key points
Worked example
Problem
A student writes: 'Oxygen is about one-fifth of the air, so it makes up about 15% of the air.' Is the percentage right? Check it, and fix it if it's wrong.
⚠ Watch out
Saying the air is mostly oxygen. Nitrogen is the biggest share, at about four-fifths; oxygen is only about one-fifth.
Memory hook
Four for N, one for O: out of five equal parts of air, about four are nitrogen and about one is oxygen. Everything else is just a sliver.
Check yourself
Without looking back: which gas sits at 80% on the line, and which at 20%? Name one gas in the 'small proportion' group, and say how long the proportions have been much the same.
Flashcards
(6)Which gas makes up the biggest share of today's atmosphere?
About what fraction of today's atmosphere is oxygen?
Name three kinds of gas found in small proportions in today's atmosphere.
For how long have the proportions of gases in the atmosphere been much the same as today?
Oxygen is about one-fifth of the air. Is that one of the big shares, or one of the small proportions?
Roughly how many times more nitrogen than oxygen is there in the air?
Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.
Learning with Lightbulb is opening soon
You can use this lesson now. Join the waitlist and we'll let you know when the full Lightbulb experience is ready.
Keep me postedMore AQA GCSE Chemistry topics
- Alternative methods of extracting metals (HT)
- Atmospheric pollutants from fuels
- Atom economy
- Atoms, elements and compounds
- Calculating rates of reactions
- Carboxylic acids (chem only)
- Cells and batteries (chem only)
- Chemical bonds (ionic, covalent, metallic)
- Collision theory and activation energy
- Concentration in mol/dm3 (chem HT)
- Conservation of mass and balanced equations
- Covalent bonding
How this lesson was checked. This AQA GCSE Chemistry (specification 8462)lesson was published through Lightbulb Learning's human-designed editorial process — the educational standards, accuracy rules and publication checks it must pass were authored and approved by Philip Halpin. It passed subject-specific assessment, automated educational checks and technical publication verification before going live (publication checks completed 29 September 2026). Published pages are monitored, human spot-checking is ongoing across the lesson library, and anything found wrong is corrected or withdrawn. How our lessons are made and checked. Spotted a mistake? Email hello@lightbulblearning.co and we'll review it.