Atomic structure and the periodic table
The arrangement of electrons explains the whole periodic table: why groups behave alike and why trends run down them.
Lesson overview
What you'll learn in this lesson
Relate atomic structure and bonding to the properties of substances.
Key learning points
- • Inside the atom
- • Electronic structure
- • Group trends
This lesson at a glance
- 30 minutes
- 20 parts to scroll through
- 4 quick checks
- Marked quiz at the end
- Gentle pace: short sittings with pauses
Words to know
Scroll down — the lesson carries on below
Watch & discover
Part 1 of 20
Visual introductionPicture this
Atomic structure and the periodic table
The arrangement of electrons explains the whole periodic table: why groups behave alike and why trends run down them.
In a nutshell
Relate atomic structure and bonding to the properties of substances.
Learning cycle
Part 2 of 20
Learning cycle 1 of 2
Part 1 · Inside the atom
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 3 of 20
Learn
Inside the atom
Protons have relative charge +1 and mass 1, neutrons 0 and 1, electrons −1 and negligible mass. Atomic number is the number of protons and defines the element; mass number is protons plus neutrons. Isotopes are atoms of the same element with different numbers of neutrons, so they share chemical properties.
Reset break
Part 4 of 20
Pause
That's sitting 1 of 5 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.
Explore the idea
Part 5 of 20
Learn
Electronic structure
Electrons occupy shells holding 2, 8, 8 for the first twenty elements, so sodium is 2,8,1. The number of outer electrons equals the group number and determines chemical behaviour, while the number of occupied shells gives the period.
Quick check
Part 6 of 20
Quick check
Part 7 of 20
Reset break
Part 8 of 20
Pause
That's sitting 2 of 5 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.
Learning cycle
Part 9 of 20
Learning cycle 2 of 2
Part 2 · Group trends
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 10 of 20
Learn
Group trends
Group 1 metals become more reactive down the group, because the outer electron is further from the nucleus and more shielded, so it is lost more easily. Group 7 non-metals become less reactive down the group, for the mirror reason: gaining an electron becomes harder. Group 0 gases are unreactive because their outer shells are full.
Quick check
Part 11 of 20
Reset break
Part 12 of 20
Pause
That's sitting 3 of 5 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.
Quick check
Part 13 of 20
Explore the idea
Part 14 of 20
Worked example
Worked answer: explain why potassium is more reactive than lithium (3 marks)
Both are group 1 metals with one outer electron, and their reactions involve losing it (1). Potassium's outer electron is in a shell further from the nucleus and is shielded by more inner shells, so the attraction between the nucleus and that electron is weaker (1). The electron is therefore lost more easily, making potassium the more reactive metal (1). 'Potassium is bigger' alone earns nothing without the effect on attraction.
Challenge round
Part 15 of 20
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
Reset break
Part 16 of 20
Pause
That's sitting 4 of 5 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.
Challenge round
Part 17 of 20
Game · Fill the gaps
Finish the sentences
Choose the word that belongs in each gap.
____ number is the number of protons and defines the element; mass number is protons plus neutrons.
Isotopes are atoms of the same element with different numbers of neutrons, so they share chemical ____.
Challenge round
Part 18 of 20
Game · Recall cards
Atomic number is the number of
Card 1 of 4
Mastery quiz
Part 19 of 20
Marked quiz
End of lesson quiz: Atomic structure and the periodic table
4 questions, marked with the reasoning shown. No timer.
1. Atomic number is the number of
2. Isotopes differ in the number of
3. Sodium's electronic structure is
4. Group 0 elements are unreactive because they have
Lesson round-up
Part 20 of 20
Lesson round-up
Ready when you are
Quiz score
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Points this lesson
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Luna: 0 out of 4 on the practice checks. Only if you feel up to it — one more?
Ask LunaPart 1 of 20 · Watch & discover