noun

isomer

EYE-suh-mer

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Isomer (noun) means a chemical compound that shares its molecular formula with another compound but has a different arrangement of atoms. Example: “Glucose and fructose are isomers of one another.”

noun

technical A chemical compound that shares its molecular formula with another compound but has a different arrangement of atoms.

"Glucose and fructose are isomers of one another."

"The two isomers behave very differently in the body despite sharing a formula."

"Chemists separated the mixture into its individual isomers."

technical An atomic nucleus that shares its mass number and atomic number with another nucleus but differs in its radioactive behaviour.

"The excited nucleus decays into a more stable isomer."

"Technetium-99m is a well-known nuclear isomer used in medical scans."

"Some nuclear isomers persist for an unusually long time before decaying."

How to use isomer

Learner’s notes

In plain EnglishTwo or more things built from exactly the same parts but put together differently.

When to use it

Isomer is a technical term used in chemistry and physics rather than everyday speech.

Memory tip

Isomer is easily confused with the similar-sounding word isotope, but the two describe different chemical concepts.

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Easily confused with

isotope →

Common pairings

structural isomer an isomer of separate the isomers

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C2 · Advanced serendipity Fortunate discoveries made entirely by accident.

Gen Z slang rizz Charm — the ability to attract a romantic interest.

B2 · Intermediate empathy The capacity to share another person’s feelings.

C1 · Advanced nonchalant Casually calm and relaxed; unconcerned.

Internet slang delulu Delusional — believing something against the odds.

Etymology nostalgia Greek nostos “return home” + algos “pain”.

C2 · Advanced serendipity Fortunate discoveries made entirely by accident.

Gen Z slang rizz Charm — the ability to attract a romantic interest.

B2 · Intermediate empathy The capacity to share another person’s feelings.

C1 · Advanced nonchalant Casually calm and relaxed; unconcerned.

Internet slang delulu Delusional — believing something against the odds.

Etymology nostalgia Greek nostos “return home” + algos “pain”.

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Fill the gap

Can you complete this real example?

Glucose and fructose are _____ of one another.

Etymology

Isomer is built from the combining form iso-, meaning equal, joined to -mer, relating to a part or unit. The formation reflects that an isomer is made of the same parts as another compound, just arranged differently.

Origin: English

Synonyms

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nuclear isomer

Rhymes for isomer

omer comer homer gomer boomer goomer bloomer newcomer customer astronomer

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Frequently asked questions

What is an isomer?

An isomer is one of two or more chemical compounds that share the same molecular formula but differ in how their atoms are arranged.

Are isomers the same substance?

No, isomers have identical formulas but different structures, so they can behave quite differently as substances.

What is a nuclear isomer?

A nuclear isomer is one of two or more atomic nuclei that share the same mass number and atomic number but differ in their radioactive behaviour.

What is the meaning of isomer?

"isomer" (noun) means a chemical compound that shares its molecular formula with another compound but has a different arrangement of atoms.