Mendeleev: gaps and testable predictions
導入済み| English | 意味 |
|---|---|
| prediction/prɪˈdɪkʃn/ | 予測 |
| atomic weight/əˈtɒmɪk weɪt/ | 原子量 |
What would explain this observation?
- An empty position can make a scientific classification stronger when it predicts what an undiscovered element should be like. Mendeleev treated recurring properties as evidence rather than filling every gap.
- Start with a prediction 预测. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Early classifications ordered elements by atomic weight 原子量 before protons, neutrons and electrons were known. Tables were incomplete, and strict mass ordering sometimes put elements into groups with unlike properties. Mendeleev left gaps for undiscovered elements and reversed mass order in some places to retain chemically sensible groups. He used neighbours to predict properties of elements expected in those gaps.
- prediction: A stated expected outcome that can be compared with new evidence; atomic weight: The historical term used for relative atomic mass in early periodic classifications.
What supported Mendeleev’s gaps?
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Mendeleev left gaps and predicted the missing elements' properties; when gallium and germanium were discovered matching those predictions, the table gained acceptance. He knew nothing of electron configuration.
Match each technical term to its precise meaning.
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Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Later discoveries filled gaps with elements whose properties agreed with the predictions, supporting the classification. Modern order follows atomic number rather than relative atomic mass. Isotopes explain why average mass need not rise strictly with proton number: different isotope masses and abundances influence the mean. The historical improvement was evidence-based prediction, not knowledge of electron shells that had yet to be discovered.
- Compare a supplied early table with a modern periodic table. Identify a gap or reversed pair, write the property pattern and decide what discovery would support or challenge the prediction. Use fictional property values for numerical interpolation and label them as such. Agreement with one predicted property is useful evidence but not proof that every aspect of a model is correct.
Which two habits make the investigation or model in this case more defensible?
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Stating the conditions and assumptions lets others repeat the work exactly, and recording the supporting evidence lets them check the conclusion. Hiding disagreeing results removes the evidence that could challenge a wrong conclusion, and one measurement can never establish a wider claim.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: in a fictional series a gap lies between densities 4.8 and 6.0 g/cm³. A simple midpoint estimate is (4.8+6.0)/2 = 5.4 g/cm³. A discovered value of 5.5 differs by 0.1 g/cm³. This demonstrates a testable interpolation, not Mendeleev’s actual historical data or a universal linear law.
Find the midpoint of fictional densities 4.0 and 6.0 g/cm³. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
Find the midpoint of fictional densities 4.0 and 6.0 g/cm³.
難易度 2/5 · 140 コイン + 今日初回完了時に小ボーナス付与
The result is 5 g/cm³. Known: densities 4.0 and 6.0 g/cm^3. Midpoint = (4.0 + 6.0)/2 = 5.0 g/cm^3. A prediction like this can be tested against the discovered element's measured density.
Check the conclusion and its limits
- Mendeleev did not arrange by known proton number. Leaving gaps was a reasoned prediction rather than accidental omission. Isotopes help explain mass-order anomalies; they do not imply the same element occupies several different proton-number positions.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Mendeleev originally ordered the table using measured proton numbers. This claim is false: Proton numbers were unknown in 1869 - Mendeleev ordered elements mainly by atomic weight and properties, and the weight-order anomalies were only explained later by isotopes.
Mendeleev: gaps and testable predictions: Later discoveries filled gaps with elements whose properties agreed with the predictions, supporting the classification. Modern order follows atomic number rather than relative atomic mass. Isotopes explain why average mass need not rise strictly with proton number: different isotope masses and abundances influence the mean. The historical improvement was evidence-based prediction, not knowledge of electron shells that had yet to be discovered.
Mendeleev originally ordered the table using measured proton numbers.
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Proton numbers were unknown in 1869 - Mendeleev ordered elements mainly by atomic weight and properties, and the weight-order anomalies were only explained later by isotopes.
A stated expected outcome that can be compared with new evidence: write the technical term.
難易度 1/5 · 100 コイン + 今日初回完了時に小ボーナス付与
prediction means A stated expected outcome that can be compared with new evidence.