A

Alpha Particles

⁴₂He (2p + 2n, charge = +2e)
Quick Reference
Formula / Notation⁴₂He (2p + 2n, charge = +2e)
Also Known AsAlpha radiation, α-ray, helium nucleus, ⁴He²⁺

What is Alpha Particles?

Alpha particles are positively charged particles identical to helium-4 nuclei, consisting of two protons and two neutrons bound together. They are emitted by heavy radioactive nuclei such as uranium and radium, and are the least penetrating but most ionising form of nuclear radiation.

Formula & Notation

⁴₂He (2p + 2n, charge = +2e)

Other Names / Synonyms: Alpha radiation, α-ray, helium nucleus, ⁴He²⁺

Properties & Characteristics

Alpha particles are positively charged nuclear fragments identical to helium-4 nuclei. They have a mass of approximately 6.644 × 10⁻²⁷ kg and a kinetic energy typically in the range of 4–9 MeV when emitted from nuclei. Their high mass results in rapid energy loss through ionizing collisions with matter, limiting their range in air to ~5 cm.

Uses & Applications

Used in radiometric dating (e.g., uranium-lead and thorium-lead methods), industrial thickness gauges, and as probes in nuclear reaction studies. Alpha-emitting radionuclides are investigated as payloads in targeted radiotherapy for cancer treatment.

Safety Information

External alpha exposure is largely harmless because particles are stopped by dead skin layers. Internal contamination from inhalation or ingestion is highly dangerous; strict radiological controls are required when handling open alpha sources.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Alpha Particles
Formula ⁴₂He (2p + 2n, charge = +2e)
Synonyms Alpha radiation, α-ray, helium nucleus, ⁴He²⁺

Frequently Asked Questions

Alpha particles are positively charged particles identical to helium-4 nuclei, consisting of two protons and two neutrons bound together. They are emitted by heavy radioactive nuclei such as uranium and radium, and are the least penetrating but most ionising form of nuclear radiation.

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