What Are Atoms Like?
- Atoms are very small things. The diameter of individual atoms range from 0.9 to 6.6 angstroms, or ten-billionths of a meter. A red blood cell, at one-millionth of a meter long, contains trillions of atoms. An atom is too small to see with light, as the shortest wavelengths of visible light are 5,000 times too long. Devices such as scanning tunneling microscopes create pictures of atoms by measuring them with tiny electrical currents.
- An atom consists of an inner nucleus of protons and electrons surrounded by a cloud of electrons. The atom's nucleus is 10,000 times smaller than the atom, meaning most of the atom is empty space. Nothing lies between the nucleus and the electrons. Forces between the nucleus and the electrons maintain the atom's size. If these forces were weaker, all objects in the universe would be much smaller, though they would weigh the same.
- An atom is not hard like a ball-bearing; it is soft like a sponge. The electrons that form the atom's outer edge move constantly but give the atom no distinct surface. Atoms in substances stretch and compress depending on how they attach to their neighbors. The hardness of some substances comes from the strength of the connections between atoms.
- The atoms in the paper clip on your desk are in constant motion, even if the paper clip seems perfectly still. The energy from heat causes atoms to jostle and bump each other at very small distances. At absolute zero, an unattainably low temperature, the motions from heat disappear, though atoms still move slightly due to other forces. Inside the atom, the electrons, neutrons and protons are also constantly moving.
