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.


Element 111, also called unununium (Uuu), chemical element with atomic number 111. It is produced artificially by nuclear fusion (in which a chemical element with larger atoms is produced by fusing together smaller atoms from other elements). Each unununium atom has a very large nucleus, or central mass, containing positively charged particles called protons and neutral particles called neutrons (see Atom). The large number of particles in the nucleus makes the atom unstable and causes the atom to split apart into smaller components soon after it is created. Scientists gave unununium its temporary name according to a system that uses Latin prefixes for the atomic number (un = 1, un = 1, un = 1), followed by the suffix -ium. Unununium was first discovered in 1994 by scientists at the Heavy-Ion Research Laboratory in Darmstadt, Germany.

Unununium has the atomic number 111, which means that each Uuu atom contains 111 protons in the nucleus. Scientists at the Heavy-Ion Research Laboratory created an atom of unununium that contained 161 neutrons, labeled unununium-272 (111 protons + 161 neutrons = unununium-272).

Unununium was created by nuclear fusion of the smaller elements bismuth (Bi) and nickel (Ni). Because the unununium nucleus contains so many particles, unununium is unstable and undergoes spontaneous fission, a process in which the atom breaks into smaller “daughter” components. When the atom splits, it releases energy in the form of electromagnetic waves and electrically charged bits of matter. This energy is known as radiation (see Radioactivity). Unununium-272 has a very brief lifespan that is 0.003 seconds. By 1998 unununium-272 was the only confirmed isotope of Element 111. Other isotopes of element 111 would be forms of the element with the same number of protons in the nucleus, but a different number of neutrons.

Unununium belongs to Group 11 (Ib) on the periodic table, which also contains the naturally occurring elements copper (Cu), silver (Ag), and gold (Au). Copper, silver, and gold all have the ability to conduct heat and electricity, and to form alloys with other metals. Because elements in the same group, or column, on the periodic table often share similar properties (a pattern known as the periodic law), scientists expect unununium to share properties with other Group 11 elements. However, because of the very limited amount of unununium that has been produced and its extremely short lifespan, scientists have been unable to determine chemical properties of this unstable element.