What is in an atom?

An atom is the smallest constituent unit of ordinary matter that has the properties of a chemical element. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. Atoms are extremely small; typical sizes are around 100 picometers (a ten-billionth of a meter, in the short scale). read more

Some matter is either smaller or larger than an atom. Examples of chemical species that are not typically considered atoms includes particles that are components of atoms: protons, neutrons, and electrons. read more

An atom's electron configuration is the orbital description of the locations of the electrons in a typical atom. Using the electron configuration and principles of physics, chemists can predict an atom's properties, such as stability, boiling point and conductivity. Typically, only the outermost electron shells matter in chemistry. read more