Chemistry · KS3 Y9 · The Periodic Table

Mendeleev's gaps

Mendeleev's gapsFree2:46Heddy Score 3 of 7, below the standard
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What you need to know

  • Mendeleev left spaces where patterns suggested that undiscovered elements should belong.
  • He used neighbouring elements to predict properties of the missing elements.
  • Later discoveries matching those predictions strengthened confidence in his periodic table.

In this clip

Runs 2:46, from 0:42 to 3:28 of the full video.

Heddy Score3/7, 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.
★ passed · ☆ pending · ✕ failed
Our students

Not enough students yet

Our own students' answers. These are what move ★7 Proven.
On YouTube

3.71M views · 28.2K likes · TED-Ed 23M subscribers

As reported by YouTube on 2026-11-02. Not part of the Heddy Score.
How the Heddy Score works

Why we picked it

The predicted element provides a concrete example of how Mendeleev tested his table.

TED-Ed on YouTubechecked 2026-10-18

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