Oxygen
Syre
ChemistryCommon
Discovered 1772 · C. W. Scheele
SPARKON07 / 10
Oxygen
The ideaOxygen has 6 outer electrons and wants 2 more, so it reacts with almost everything.
O · atomic number 8 · shells 2, 6
Lets you predictIt gains 2 electrons (O²⁻) in ionic compounds, or shares 2 in molecules like H₂O.
Tests usually ask
- Electron shells and ions
- Burning = reacting with oxygen
Scan for the full explanation and a practice question.
SPARKON · 07 / 10
SPARKON · 07 / 10
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Chemistry ● Common: a core idea every course needs
Oxygen
Oxygen has 6 outer electrons and wants 2 more, so it reacts with almost everything.
O · atomic number 8 · shells 2, 6
Why it works
Common card because oxygen is common: it is about a fifth of the air and almost half of the mass of Earth's crust, locked into rock and water.
Scheele found it in his pharmacy lab in Sweden, but his book came out late, so Priestley in England often gets the credit.
What it lets you predict
It gains 2 electrons (O²⁻) in ionic compounds, or shares 2 in molecules like H₂O.
How tests ask about it
- Electron shells and ions
- Burning = reacting with oxygen
Try it
How many electrons does an oxygen atom need to fill its outer shell, and what ion forms if it gains them?
Show the answer
It has 6 outer electrons and needs 2 more. Gaining them gives the oxide ion, O²⁻, as in magnesium oxide. In molecules such as water, oxygen shares electrons instead.
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