Atomic Structure and Subatomic Particles
This page introduces the fundamental concepts of atomic structure and subatomic particles. It explains that all substances are composed of atoms, which contain three subatomic particles: protons, neutrons, and electrons. The page provides details on the relative mass and charge of these particles, as well as their locations within the atom.
Definition: An atom is the smallest unit of matter that retains the properties of an element.
The nucleus of an atom is described as having a radius of about 1x10^-14 m, containing protons and neutrons, and carrying a positive charge. It also concentrates most of the atom's mass.
Highlight: The electrons move around the nucleus in shells, are negatively charged, and have virtually no mass.
The page emphasizes that while electrons are tiny, they cover a significant amount of space around the nucleus, giving atoms a radius of about 0.1 nm.