Nov 14, 2025 · An atom is the basic building block of chemistry. It is the smallest unit into which matter can be divided without the release of electrically charged particles.

This diagram plots the absolute magnitude of stars on the vertical axis and the spectral type (effectively measuring color or temperature) on the horizontal axis.

The hydrogen nuclei that combine to form heavier helium nuclei must lose a small portion of their mass (about 0.63 percent) in order to “fit together” in a single larger atom. They lose this mass …

An atom is the basic building block of chemistry. It is the smallest unit into which matter can be divided without the release of electrically charged particles.

Below is the article summary. For the full article, see atom. The classical “planetary” model of an atom. The protons and neutrons in the nucleus are circled by electrons in “orbit” around the …

Explore an atom's interior to discover the layout of its nucleus, protons, and electrons.

Emeritus Professor of Philosophy, Catholic University of Nijmegen, The Netherlands. Author of From Atomos to Atom and others.

All atoms have the same basic parts. These are a nucleus and at least one particle called an electron. The nucleus contains protons and neutrons. Diagrams of two kinds of atoms show …

An atom is the smallest piece of matter that has the characteristic properties of a chemical element, such as hydrogen, oxygen, calcium, iron, gold, and neon. More than 90 types of atom …

If the atom emits energy, the electron falls into a more stable orbit closer to the nucleus. The diagram can be constructed by representing various energy levels (or states) with horizontal …