Category
Chemistry
Explore the 16 entries currently assigned to this category. These counts describe this curated catalogue, not the size or rate of change of the field itself.
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Not a fact anymore
Carbon has only two true crystalline forms: diamond and graphite.
What we know now
Carbon can form many allotropes—different structures made entirely from the same element. Diamond and graphite are two examples, but carbon also forms fullerenes, carbon nanotubes, graphene, and other structures with very different shapes and properties.
- Status
- Overturned
- Category
- Chemistry
- Accepted for
- ≈235 years
- Changed approximately
- 1985–2004
Not a fact anymore
Noble gases are completely inert and cannot form stable chemical compounds.
What we know now
Noble gases are usually very unreactive, but some can form stable compounds. Xenon has the richest chemistry, and compounds involving krypton, radon, and argon are also known under suitable conditions.
- Status
- Overturned
- Category
- Chemistry
- Accepted for
- ≈67 years
- Changed approximately
- 1962 onward
Not a fact anymore
Rubber, cellulose, and other polymers are loose aggregates of small molecules rather than giant covalently bonded molecules.
What we know now
Polymers are macromolecules: very large molecules made from many smaller building blocks joined by covalent bonds into long chains or networks. Materials such as rubber and cellulose are not merely loose clusters of ordinary small molecules.
- Status
- Overturned
- Category
- Chemistry
- Accepted for
- ≈45 years
- Changed approximately
- 1920s–1930s
Not a fact anymore
Oxidation always means adding oxygen to a substance.
What we know now
Oxidation does not require oxygen. In modern chemistry, oxidation means that a substance loses electrons, or equivalently that its oxidation state increases. Oxygen often causes oxidation, but chlorine, metal ions, and many other chemicals can do the same.
- Status
- Superseded
- Category
- Chemistry
- Accepted for
- ≈135 years
- Changed approximately
- Late 19th–20th century
Not a fact anymore
All atoms of the same chemical element have identical mass.
What we know now
An element can contain several isotopes. Its isotopes have the same number of protons but different numbers of neutrons, giving them different masses.
- Status
- Overturned
- Category
- Chemistry
- Accepted for
- ≈98 years
- Changed approximately
- 1910s–1920s
Not a fact anymore
Stable organic free radicals cannot be isolated.
What we know now
Some free radicals are sufficiently persistent to be prepared, stored, crystallized, and studied. Their stability can result from resonance, steric protection, electronic effects, or delocalization of the unpaired electron across the molecule.
- Status
- Overturned
- Category
- Chemistry
- Accepted for
- ≈50 years
- Changed approximately
- 1900–1930s
Not a fact anymore
Fermentation requires intact living cells and cannot occur in a cell-free extract.
What we know now
Fermentation is carried out by enzymes and metabolic pathways that can continue outside intact cells when the necessary cellular components and conditions are preserved.
- Status
- Overturned
- Category
- Chemistry
- Accepted for
- ≈47 years
- Changed approximately
- 1897–1907
Not a fact anymore
At chemical equilibrium, the forward and reverse reactions have stopped.
What we know now
Chemical equilibrium is dynamic. Forward and reverse processes continue at equal rates, leaving concentrations and other macroscopic properties approximately constant.
- Status
- Overturned
- Category
- Chemistry
- Accepted for
- ≈14 years
- Changed approximately
- Late 19th–20th century
Not a fact anymore
Organic compounds can be produced only by living organisms using a special vital force.
What we know now
Organic molecules follow the same chemical principles as other matter and can be synthesized from nonliving starting materials. Laboratories and industry routinely make both natural and entirely new organic compounds.
- Status
- Superseded
- Category
- Chemistry
- Accepted for
- ≈43 years
- Changed approximately
- 1828–late 19th century
Not a fact anymore
Two substances with the same molecular formula must be the same compound.
What we know now
Different compounds can share a molecular formula while differing in atom connectivity or three-dimensional arrangement. These isomers can have very different physical, chemical, and biological properties.
- Status
- Overturned
- Category
- Chemistry
- Accepted for
- ≈43 years
- Changed approximately
- 1820s–1830s
Not a fact anymore
Every acid contains oxygen.
What we know now
Many acids contain oxygen, but some do not. Hydrochloric acid, hydrobromic acid, and hydroiodic acid are familiar counterexamples.
- Status
- Overturned
- Category
- Chemistry
- Accepted for
- ≈35 years
- Changed approximately
- 1810s
Not a fact anymore
Base metals are immature or imperfect forms of metal that naturally ripen toward gold, and alchemical processes can accelerate that maturation.
What we know now
Copper, iron, lead, silver, gold, and other metals are distinct chemical elements defined by atomic number. Ordinary chemical reactions cannot turn one element into another; elemental transmutation requires nuclear processes.
- Status
- Superseded
- Category
- Chemistry
- Accepted for
- Not quantified
- Changed approximately
- 17th–19th centuries
Not a fact anymore
Burning substances release a fire-like material called phlogiston.
What we know now
Combustion is a set of chemical oxidation reactions. In ordinary burning, a fuel reacts with oxygen and forms new products while releasing energy.
- Status
- Superseded
- Category
- Chemistry
- Accepted for
- ≈104 years
- Changed approximately
- 1770s–1790s
Not a fact anymore
Metals are composed from sulfur and mercury principles in different proportions and qualities.
What we know now
Metals are chemical elements or alloys whose properties arise from atomic structure, composition, crystal structure, bonding, defects, and microstructure. They are not built from universal sulfur and mercury principles.
- Status
- Superseded
- Category
- Chemistry
- Accepted for
- Not quantified
- Changed approximately
- 17th–18th centuries
Not a fact anymore
Water is a fundamental element that cannot be decomposed into simpler substances.
What we know now
Water is a chemical compound with the formula H2O. It can be formed from hydrogen and oxygen and can be decomposed into those elements.
- Status
- Overturned
- Category
- Chemistry
- Accepted for
- ≈2,133 years
- Changed approximately
- 1780s
Not a fact anymore
Air is a single elemental substance.
What we know now
Air is a mixture of gases, mainly nitrogen and oxygen, with smaller amounts of argon, carbon dioxide, water vapor, and other gases.
- Status
- Overturned
- Category
- Chemistry
- Accepted for
- ≈2,124 years
- Changed approximately
- 1750s–1780s
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