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Valence Electrons

Part of the Atomic Structure section of Coddy's Chemistry journey. Lesson 21 of 45.

The electrons in the outer shell are the valence electrons. They decide how an atom reacts. Sodium, 2, 8, 1, has 1.

A sodium atom with its single outer electron ringed

Sodium: 1 valence electron

The same number of valence electrons means similar behavior: lithium, sodium and potassium all have 1, and all fizz in water.

A full outer shell, as in neon (2, 8) and argon (2, 8, 8), makes an atom hardly react. Helium is full with 2.

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Challenge

Phosphorus, with 15 electrons, glows in the dark and is in the tip of every match. Fill its shells to find its valence electrons.

Try it yourself

Electron shellsFill the electrons of P (phosphorus)
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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