GCSE · Chemistry · Edexcel · Spec 1CH0

Comparing the size of nanoparticles with atoms and molecules

Shrink a metre by a thousand, three times over, and you land on the nanometre: the unit that measures your DNA. Where do atoms, dust and cells sit around it?

Size scale · atoms to a plant cell

Tap each chip, smallest to biggest. Each tick is 100 times bigger than the one before, so this is a log scale: a normal ruler would squash everything except the plant cell into one spot. A range sits at its middle.

Atom (radius / bond length)

about 10⁻¹⁰ m

A typical atom radius and bond length are about 10⁻¹⁰ m. That is almost 10 times smaller than the smallest nanoparticle, so atoms sit below the nano band.

Chemistry · The prefixes

Shrink a metre by a thousand — three times

how big a division of a metre each prefix makes

1 · Biggest division4 · Smallest division

nano-
milli-
pico-
micro-

Watch out: Micro and nano are easy to swap. Micro is the step before nano, and it is a thousand times bigger.

Worked example · nanometres into metres

Problem

Write 2 nm in metres in standard form. Then do the same for 100 nm, which needs one extra move.

Chemistry · Size classes

Which size class is it?

Pick a particle, then pick the box it belongs in. Check the size first, in nanometres or metres.

Still to sort

Smaller than a nanoparticle (0)

Under 1 nm. A typical atom is down here.

Where the line is: Nanoparticles start at 1 nm (10⁻⁹ m). A typical atom radius is about 10⁻¹⁰ m, almost 10 times smaller.

Nanoparticle (0)

1 to 100 nm

Where the line is: Go over 100 nm and you have left the nanoparticles for the fine particles.

Fine particle (0)

Over 100 nm, up to 2.5 × 10⁻⁶ m (PM2.5)

Where the line is: At 2.5 × 10⁻⁶ m the coarse particles begin.

Coarse particle (0)

2.5 × 10⁻⁶ to 1 × 10⁻⁵ m (PM10)

Where the line is: Technically these are microparticles too, but they are still far smaller than a plant cell.

Larger microparticle (0)

Plant-cell scale. Microparticles span 1 × 10⁻⁶ to 1 × 10⁻³ m.

Where the line is: Coarse particles count as microparticles, but a plant cell is about 20 times wider than the top of the coarse range.

6 of 6 still to sort.

Watch out: 100 nm is still a nanoparticle. Fine particles start just above it.

Chemistry · Atoms vs nanoparticles

Is a single atom a nanoparticle?

A classmate says: "Nano just means really tiny, so a single atom must be a nanoparticle."

Which is closest to what you think?

Yes. Atoms are tiny, so they count as nanoparticles. Nano means atom-sized.No. Atoms are bigger than nanoparticles, because nanoparticles are the tiniest things there are.Micro and nano mean the same thing. Both are about the size of an atom.No. An atom is about 10⁻¹⁰ m, almost 10 times smaller than the smallest nanoparticle at 10⁻⁹ m, so nanoparticles are bigger than atoms.

How sure are you?

I'm sureI think soI'm guessing

Yes. Atoms are tiny, so they count as nanoparticles. Nano means atom-sized.

This is a common misconception

Tiny is not the test. A nanoparticle is 1 to 100 nm in size. A typical atom radius is about 10⁻¹⁰ m, almost 10 times smaller than the smallest nanoparticle. Individual atoms are not nanoparticles.

No. Atoms are bigger than nanoparticles, because nanoparticles are the tiniest things there are.

This is a common misconception

Right verdict, wrong reason. It's the other way round: atoms are smaller. Nanoparticles are larger than atoms, and the smallest one (1 nm = 10⁻⁹ m) is almost 10 times bigger than a typical atom (about 10⁻¹⁰ m).

Micro and nano mean the same thing. Both are about the size of an atom.

This is a common misconception

They are two steps apart. Each prefix step is a thousand times smaller, and micro comes just before nano, so a nanometre is a thousand times smaller than a micrometre. And neither is atom-sized: the smallest nanoparticle is almost 10 times bigger than an atom.

No. An atom is about 10⁻¹⁰ m, almost 10 times smaller than the smallest nanoparticle at 10⁻⁹ m, so nanoparticles are bigger than atoms.

This matches the evidence

Exactly. The nanoparticle band is 1 to 100 nm, and a typical atom sits just below the bottom of it. (Check the powers: −10 is smaller than −9.)

Nano names a size band, 1 to 100 nm. It does not mean 'as small as an atom': the smallest nanoparticle is almost 10 times bigger than a typical atom.

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

What you need to know

Starting from a metre, milli-, micro-, nano- and pico- are steps that each make the unit a thousand times smaller.
A nanometre is 10⁻⁹ m, which is one billionth of a metre.
Have a goDev is sure that a nanometre is a millionth of a metre. Which prefix has Dev actually described?
Micro-.
From a metre, every step is a thousand times smaller: milli is a thousandth, micro is two steps (a millionth), nano is three steps (a billionth).
Standard form is a × 10ⁿ: a is at least 1 but less than 10, and n is any whole number, positive or negative.
Nanoscience studies structures from 1 to 100 nm in size, and any particles in that range are nanoparticles.
Human DNA is about 2 nm wide, so its width sits inside that 1 to 100 nm range.
Have a goWhich is the smaller length, 1 × 10⁻¹⁰ m or 1 × 10⁻⁹ m? Decide before you reveal.
1 × 10⁻¹⁰ m, ten times smaller.
A nanometre is 10⁻⁹ m. A power of −10 is one more step down, so the bigger the minus number, the smaller the length.
Atoms are not nanoparticles: a typical atom radius or bond length is about 10⁻¹⁰ m, almost 10 times smaller than 1 nm.
Fine particles are over 100 nm, up to 2.5 × 10⁻⁶ m; coarse particles run from there up to 1 × 10⁻⁵ m.
PM2.5 and PM10 are labels for a particle's maximum diameter: 2.5 × 10⁻⁶ m and 1 × 10⁻⁵ m (10 µm).
Microparticles span 1 × 10⁻⁶ to 1 × 10⁻³ m. Coarse particles and plant cells (about 2 × 10⁻⁴ m) both count.
Have a goA plant cell is about 2 × 10⁻⁴ m long and the biggest coarse particle is 1 × 10⁻⁵ m across. About how many times wider is the cell?
About 20 times.
2 × 10⁻⁴ is 20 × 10⁻⁵, so the powers differ by one (a factor of 10) and the 2 doubles it. Not 2 times, and not 200.

The big picture

A nanoparticle is 1 to 100 nm in size, which is 10⁻⁹ to 10⁻⁷ m. That makes it bigger than an atom (about 10⁻¹⁰ m) and smaller than fine particles, coarse dust and a plant cell. Learn the size bands, and learn to write each size in metres in standard form.

Key points

1Nano is the third prefix step below a metre: 10⁻⁹ m, one billionth of a metre.

2The nanoparticle band is 1 to 100 nm. Fine particles are bigger than that; coarse particles bigger still.

3Atoms are not nanoparticles: a typical atom (about 10⁻¹⁰ m) is almost 10 times smaller than the smallest one.

4To convert nm to m, swap in × 10⁻⁹ m, then tidy the front number so it is at least 1 and less than 10.

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Worked example

Problem

A particle is 2.5 × 10⁻⁶ m across. Give its size in nanometres, then say where it sits on the scale.

⚠ Watch out

'Nano' does not mean atom-sized. A typical atom is about 10⁻¹⁰ m, and the smallest nanoparticle is 10⁻⁹ m. That is almost ten times bigger, and the whole gap hides in one small minus-number.

🧠

Memory hook

Milli, micro, nano, pico: each one a thousand times smaller than the last. And the smallest nanoparticle is still almost ten times bigger than an atom.

✓

Check yourself

A particle is 6 × 10⁻⁷ m across. Write its size in nanometres, then say whether it is a nanoparticle, a fine particle or a coarse particle, and why.

Flashcards

(12)

In what order do the prefixes milli-, micro-, nano- and pico- divide up a metre?

Milli, then micro, then nano, then pico. Each step is a thousand times smaller than the step before.

What is a nanometre?

A unit for very small distances: 10⁻⁹ m, or one billionth of a metre.

What is standard form?

a × 10ⁿ, where a is at least 1 and less than 10 and n is any positive or negative integer. It saves writing out all the zeros.

What is nanoscience?

The study of structures in the nanometre region, 1 to 100 nm in size.

What is a nanoparticle?

Any particle or structure that is 1 to 100 nm in size.

How wide is human DNA?

About 2 nm, though it is much longer than it is wide.

How does a typical atom compare in size with the smallest nanoparticle?

A typical atom radius or bond length is about 10⁻¹⁰ m: almost 10 times smaller than 1 nm. Individual atoms are not nanoparticles.

What size range do fine particles cover?

Larger than 100 nm, up to 2.5 × 10⁻⁶ m. They are not quite nanoparticles.

What size range do coarse particles cover, and what else are they?

From 2.5 × 10⁻⁶ m to 1 × 10⁻⁵ m (at least 2,500 nm). Technically they are a type of microparticle.

What does PM2.5 mean?

Particulate matter with a maximum diameter of 2.5 µm (2.5 × 10⁻⁶ m).

What does PM10 mean?

Particulate matter with a maximum diameter of 10 µm (1 × 10⁻⁵ m). The label is based on the maximum possible size.

What is the microparticle range, and what is an example?

1 × 10⁻⁶ to 1 × 10⁻³ m. A plant cell, about 200 µm (2 × 10⁻⁴ m) long, is one.

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.

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Shrink a metre by a thousand — three times

Which size class is it?

Is a single atom a nanoparticle?

More Edexcel GCSE Chemistry topics