A

Atom

¹²₆C (atomic symbol notation)
Quick Reference
Formula / Notation¹²₆C (atomic symbol notation)
Also Known AsBasic unit of matter, atomic particle, element unit; from Greek: atomos (indivisible)

What is Atom?

An atom is the smallest unit of a chemical element that retains the chemical properties of that element. Atoms consist of a nucleus containing protons and neutrons, surrounded by electrons in energy levels or orbitals. Atoms combine to form molecules and compounds through chemical bonds, and are the fundamental building blocks of all matter.

Formula & Notation

¹²₆C (atomic symbol notation)

Other Names / Synonyms: Basic unit of matter, atomic particle, element unit; from Greek: atomos (indivisible)

Properties & Characteristics

An atom is the smallest unit of an element that retains its chemical properties. It consists of a dense, positively charged nucleus containing protons and neutrons, surrounded by a cloud of electrons in quantised energy levels (shells/orbitals). Atoms are electrically neutral, with the number of electrons equal to the number of protons (atomic number Z). Atomic radii are on the order of 10⁻¹⁰ m (1 Å).

Uses & Applications

The atomic theory underpins all of chemistry, materials science, and physics. Understanding atomic structure guides the design of catalysts, semiconductors, pharmaceuticals, and new materials. Isotopic variations of atoms are used in radiometric dating, medical imaging, and tracer studies.

Safety Information

Atoms of unstable (radioactive) isotopes emit ionising radiation and require radiation safety measures. Handling reactive atoms or highly reactive elemental substances (e.g., sodium, fluorine) requires specialised PPE and procedures.

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

Key Facts

Term Atom
Formula ¹²₆C (atomic symbol notation)
Synonyms Basic unit of matter, atomic particle, element unit; from Greek: atomos (indivisible)

Frequently Asked Questions

An atom is the smallest unit of a chemical element that retains the chemical properties of that element. Atoms consist of a nucleus containing protons and neutrons, surrounded by electrons in energy levels or orbitals. Atoms combine to form molecules and compounds through chemical bonds, and are the fundamental building blocks of all matter.

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