Physics · Chapter 10
⚛️ Atoms & Matter
What everything is made of.
💡 The Building Blocks
Every object — this screen, your hand, the air — is made of tiny atoms. Atoms are so small that a single grain of sand contains quintillions of them.
An atom has three parts:
• Protons (+ charge) — in the nucleus
• Neutrons (no charge) — in the nucleus
• Electrons (− charge) — orbiting around
The number of protons defines what element it is. 1 proton = hydrogen. 6 protons = carbon. 79 protons = gold.
Atoms combine into molecules. Two hydrogens + one oxygen = H₂O = water. 💧
Nuclear fission chain reaction — basis of nuclear power plantsWikimedia Commons / CC BY-SA 3.0
Chernobyl reactor 4 — worst nuclear accident (1986), cautionary exampleWikimedia Commons / CC BY-SA 3.0
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Inside an Atom
AnimationElectrons orbit the nucleus. Try changing the proton count below — you'll get a different element!
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Build an Atom
ExperimentPick a number of protons. The element name updates. The proton count is the atomic number.
ElementCarbon (C)
Protons / Electrons6 / 6
Every atom of an element has the same number of protons — that's its identity. Atoms are usually neutral, so electrons = protons.