Chemistry · KS3 Y9 · The Periodic Table
Predicting with periodic trends
Predicting with periodic trendsFree2:24Heddy Score 3 of 7, below the standard
What you need to know
- Mendeleev arranged the elements into periods and groups, putting elements that behave alike in the same group.
- He left gaps for undiscovered elements and predicted their properties, and later discoveries matched those predictions.
- Elements in the same group behave similarly because they have the same number of electrons in their outer shell.
- Atoms get bigger going down a group because each period adds another shell of electrons.
In this clip
Runs 2:24, from 0:09 to 2:33 of the full video.
Heddy ScoreSeven checks every clip must pass before students see it: trusted, on the map, accurate, focused, accessible, safe, and proven by students.3/7, Below the standard
See the seven stars
- Trusted source · passed. The creator's own upload, live and playable here.
- On the map · not judged yet. A teacher watched it: it mainly teaches this map topic.
- Spec-true · not judged yet. Accurate, and right for the current UK specification.
- Focused · passed. One idea, short enough to watch in one go.
- Accessible · passed. Good captions, clear sound and pictures.
- Safe for children · not judged yet. Right for 11 to 16 year olds, with no sales pitch.
- Proven · not judged yet. Earned from our students: they learn from it, find it helpful and watch it to the end.
Our students
Not enough students yet
Our own students' answers. These are what move ★7 Proven.On YouTube
How the Heddy Score works5.63M views · 92.4K likes · Professor Dave Explains 4.49M subscribers
As reported by YouTube on 2026-11-02. Not part of the Heddy Score.Why we picked it
A clear opening explanation of how Mendeleev used the table's patterns to predict undiscovered elements, linked to outer-shell electrons.
Professor Dave Explains on YouTubechecked 2026-10-22
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