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Isotopes

Part of the Atomic Structure section of Coddy's Chemistry journey. Lesson 16 of 45.

Atoms of one element with different numbers of neutrons are isotopes. Same protons, same chemistry, different mass.

Chlorine has two isotopes: 75% chlorine-35, with 18 neutrons, and 25% chlorine-37, with 20.

A mass spectrometer draws one peak per isotope: at its mass number, as tall as its percent of the atoms. The peaks add up to 100%.

A bar chart of chlorine: 75 percent of atoms at mass 35, 25 percent at mass 37

The mass spectrum of chlorine: one peak for each isotope

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Challenge

A mass spectrometer measures a sample of chlorine: 75% of the atoms are chlorine-35, and 25% are chlorine-37. Draw its mass spectrum.

Try it yourself

Mass spectrumThe isotopes of Cl (chlorine)
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This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Atomic Structure

1Matter and Atoms

What Everything Is Made OfElements, Compounds, MixturesChemical SymbolsCounting Atoms in a FormulaRecap - Molecule Kit

4Electron Arrangement

Shells and the First 20Valence ElectronsIonization Energy as EvidenceLight from AtomsSubshells: s, p, dAufbau, Hund and PauliWriting ConfigurationsIons and the ExceptionsRecap - Configuration Race

7Practice Problems

Recap - Potassium OxideRecap - Helium from RocksRecap - Uranium to Lead

2Models of the Atom

Dalton and ThomsonRutherford's Gold FoilThe Nuclear AtomBohr's ShellsRecap - From Ball to Nucleus

5The Periodic Table

Mendeleev's PuzzleGroups and PeriodsBlocks: s, p, d, fMetals, Non-metals, MetalloidsAlkali MetalsHalogensNoble GasesRecap - Build the Table

3Inside the Atom

Protons Decide the ElementElectrons and ChargeNeutrons and Mass NumberNuclide NotationIonsIsotopesRadioactive DecayRelative Atomic MassRecap - Mystery Particles

6Periodic Trends

Atomic RadiusIonic RadiusIonization Energy TrendElectronegativityExplaining TrendsRecap - Mystery Element