Atoms
Atoms
Atoms (/ˈætəm/; from Greek atomos, meaning 'indivisible') are the basic units of matter and the defining structure of elements. They are composed of three kinds of smaller particles: protons, neutrons, and electrons.
Etymology
The term "atom" comes from the Ancient Greek word "atomos", which means "indivisible". This term was coined by the ancient Greek philosophers Leucippus and his pupil Democritus, who proposed that matter could not be divided into smaller pieces indefinitely, but would eventually reach a point where particles were indivisible. These indivisible particles were what they called "atomos".
Structure
Atoms are composed of three types of sub-atomic particles:
- Protons - These are positively charged particles found within the atomic nucleus. The number of protons in an atom determines the atomic number and the element it represents.
- Neutrons - These are neutral particles also found within the atomic nucleus. They contribute to the atom's mass and the stability of the nucleus.
- Electrons - These are negatively charged particles that orbit the nucleus in energy levels often referred to as electron shells.
Related Terms
- Molecule - A group of atoms bonded together, representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction.
- Ion - An atom or molecule with a net electric charge due to the loss or gain of one or more electrons.
- Isotope - Each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei.
- Element - A substance whose atoms all have the same number of protons.
- Compound - A thing that is composed of two or more separate elements; a mixture.
External links
- Medical encyclopedia article on Atoms
- Wikipedia's article - Atoms
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