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SavannahYear 8
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ScienceChemistry foundations for GCSE (AQA 8462)30 min★★★ difficulty

Atoms, elements, compounds and formulae

Chemistry has a written language. Get formulae right at KS3 and GCSE equations become bookkeeping rather than guesswork.

Lesson overview

What you'll learn in this lesson

Understand atoms, elements and compounds, and the use of chemical symbols and formulae

Key learning points

  • • Symbols are not abbreviations
  • • Counting atoms in a formula
  • • Compounds have new properties
  • • Mixtures can be separated physically

This lesson at a glance

  • 30 minutes
  • 19 parts to scroll through
  • 4 quick checks
  • Marked quiz at the end
  • Gentle pace: short sittings with pauses

Words to know

elementscompoundschemicalsymbolsformulae

Scroll down — the lesson carries on below

Part 1 of 19 · Discover5%
1

Watch & discover

Part 1 of 19

Watch first

Atoms, elements, compounds and formulae

An English teaching video on this topic from Revision Monkey. Watch it, then scroll down for the lesson.

In a nutshell

Understand atoms, elements and compounds, and the use of chemical symbols and formulae

2

What you already know

Part 2 of 19

Before we start

What you already know

You should already know that matter is made of particles and that the periodic table lists elements.

3

Key words

Part 3 of 19

Key words

Words you'll need today

Element
A substance made of only one type of atom.
Compound
Two or more elements chemically bonded in fixed proportions.
Mixture
Substances together but not chemically joined.
Formula
Symbols and numbers showing the atoms in a substance.
Subscript
The small number showing how many atoms of the element before it.
4

Learning cycle

Part 4 of 19

Learning cycle 1 of 2

Reading the symbols

A short piece of teaching, then a check to make sure it has landed.

5

Explore the idea

Part 5 of 19

Learn

Symbols are not abbreviations

Each element has an agreed one- or two-letter symbol, with the second letter always lower case. CO is carbon monoxide, a compound; Co is cobalt, an element. That capital letter carries real information.

6

Explore the idea

Part 6 of 19

Learn

Counting atoms in a formula

In H2SO4 there are two hydrogen, one sulfur and four oxygen atoms. Brackets multiply everything inside: Ca(OH)2 has one calcium, two oxygen and two hydrogen. A big number in front multiplies the whole formula: 3H2O is six hydrogen and three oxygen atoms.

7

Quick check

Part 7 of 19

Quick check

How many atoms in total are in H2SO4?

8

Quick check

Part 8 of 19

Quick check

Ca(OH)2 contains how many hydrogen atoms?

9

Reset break

Part 9 of 19

Pause

That's sitting 1 of 2 done

Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.

Stop here for now
10

Learning cycle

Part 10 of 19

Learning cycle 2 of 2

Compounds versus mixtures

A short piece of teaching, then a check to make sure it has landed.

11

Explore the idea

Part 11 of 19

Learn

Compounds have new properties

Sodium is a reactive metal and chlorine a toxic gas, yet sodium chloride is table salt. A compound's properties are not the average of its elements, because bonding has changed the arrangement of the outer electrons.

12

Explore the idea

Part 12 of 19

Learn

Mixtures can be separated physically

Air, sea water and steel are mixtures: their components keep their properties and can be separated by filtration, distillation or chromatography. Splitting a compound needs a chemical reaction, usually a lot more energy.

13

Quick check

Part 13 of 19

Quick check

Which is a mixture?

14

Quick check

Part 14 of 19

Quick check

3H2O contains how many oxygen atoms?

15

Common mix-ups

Part 15 of 19

Common mix-ups

Things people often get wrong

  • CO and Co are not the same thing — capitalisation matters.
  • A compound is not a mixture: its proportions are fixed.
  • The big number in front multiplies every atom in the formula, including those in brackets.
16

Challenge round

Part 16 of 19

Game · Sort it

Which of these are true?

Drag each card into the right column. Tap a card first if dragging is fiddly.

True

Not true

17

Challenge round

Part 17 of 19

Game · Fill the gaps

Finish the sentences

Choose the word that belongs in each gap.

A compound's properties are not the average of its ____, because bonding has changed the arrangement of the outer electrons.

Splitting a compound needs a ____ reaction, usually a lot more energy.

18

Mastery quiz

Part 18 of 19

Marked quiz

End of lesson quiz: Atoms, elements, compounds and formulae

6 questions, marked with the reasoning shown. No timer.

  1. 1. An element contains...

  2. 2. Co is...

  3. 3. Separating a compound needs...

  4. 4. Sodium chloride's properties are...

  5. 5. Subscripts apply to...

  6. 6. Steel is best described as...

19

Lesson round-up

Part 19 of 19

Lesson round-up

Ready when you are

Quiz score

Not sat

Games

Not played

Points this lesson

0

Best run

0 in a row

Luna: 0 out of 4 on the practice checks. Only if you feel up to it — one more?

Ask Luna

Do the work

Your written work for this lesson

This is the part you'd do in your book at school. Pick the pieces below, write here or on paper, and photograph anything you draw or work out.

Case study

Why the school greenhouse failed

A science club grew tomato plants in the school greenhouse. In June the plants grew well: leaves were dark green and the fruit set quickly. In July the club went away for two weeks and left the greenhouse door shut. When they came back, the leaves were curled and pale and most of the fruit had dropped.

The club had a data logger inside. It showed the temperature reached 46 °C on several afternoons and the soil moisture fell close to zero. The club knew photosynthesis needs light, water and carbon dioxide, and that enzymes in a plant work best in a narrow range of temperature. Above that range the enzymes stop working properly.

The club repeated the summer with the door propped open and a water bottle drip on each pot. Temperature peaked at 31 °C and the plants survived.

Written for Good Learning Co.

Reading questions

  1. Name the variable the club changed the second time, and one variable they kept the same.
  2. Explain, using the words photosynthesis and enzymes, why the plants were damaged in July.
  3. Write a conclusion for the club's report, saying how far the evidence supports it.

  • Method and results

    Writing

    Write the aim, what you changed, what you measured and what you kept the same, then record your results in a table.

    1 page + results table

  • Conclusion

    Writing

    Explain what your results show and why, using the scientific words from the lesson. Say how you know you can trust them.

    6–8 sentences

  • Labelled diagram

    Diagram

    Draw the apparatus or the process in pencil, label it fully, and photograph it.

    1 labelled diagram

  • Reading and notes

    Reading

    Read the lesson text again and write the key ideas in your own words.

    Half a page of notes

Saved as you type.

Part 1 of 19 · Watch & discover

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