Matter & Energy

Matter is composed of atoms or groups of atoms called molecules. The arrangement of particles in a material depends on the physical state of the substance. In a solid, particles form a compact structure that resists flow. Particles in a liquid have more energy than those in a solid. They can flow past one another, but they remain close. Particles in a gas have the most energy. They move rapidly and are separated from one another by relatively large distances.

Lanthanide Series

Lanthanide Series, series of metallic elements of the periodic table commonly defined as the elements cerium (atomic no. 58) through ytterbium (atomic no. 70). Yttrium (atomic no. 39) and lanthanum (atomic no. 57) are often included in the lanthanide series. (see Chemical Elements; Rare Earth Elements).