Edexcel GCSE Chemistry · 1CH0
Specification 1.14 · Paper 1, Paper 2
Revise: Mendeleev's PredictionsRather than treating the gaps as mistakes, Mendeleev proposed that undiscovered elements belonged there.
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GCSE Chemistry · key term
An unfilled position in an arrangement of known elements, suggesting that an element had not yet been discovered.
Used by Edexcel and OCR
Specification 1.14 · Paper 1, Paper 2
Revise: Mendeleev's PredictionsRather than treating the gaps as mistakes, Mendeleev proposed that undiscovered elements belonged there.
Paper 1 (Foundation), Paper 2 (Foundation), Paper 3 (Higher), Paper 4 (Higher)
A space deliberately left in Mendeleev’s Periodic Table for an element that had not yet been discovered.
Revise: Support for Mendeleev's ideasWhere the pattern suggested that an element was missing, he left a gap rather than putting a known element in the wrong group. He then used the properties of neighbouring elements to predict what the missing element would be like.
Link a gap in Mendeleev’s table to a prediction: the pattern of neighbouring elements let him estimate the missing element’s properties.
For a question about Mendeleev’s gaps, link prediction to evidence: he predicted the properties of an undiscovered element, and a later discovery had similar properties.
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