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.


Nobelium, symbol No, radioactive metallic element with an atomic number of 102. Nobelium is one of the transuranium elements in the actinide series of the periodic table. The element is named for the Swedish inventor and philanthropist Alfred Bernhard Nobel.

Nobelium is not found in nature but is produced artificially in the laboratory. Separate discovery of the element was first claimed in 1957 by scientific groups in the United States, Britain, and Sweden, but the first confirmed discovery of a nobelium isotope, by a team of scientists at the Lawrence Berkeley National Laboratory in Berkeley, California, took place in 1958. The isotope was created by bombarding curium isotopes with carbon ions.

Chemically, the properties of nobelium are unknown, but because it is an actinide, its properties should somewhat resemble those of the rare earth elements. Isotopes with mass numbers from 250 to 259 and 262 are known. The most stable isotope, nobelium-259, has a half-life of 58 minutes. The most common isotope, nobelium-255, has a half-life of a few minutes. See also Radioactivity.