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.


Bohrium, symbol Bh, chemical element with atomic number 107. It is produced artificially by nuclear fusion (in which an element with larger atoms is produced by fusing together smaller atoms of other elements). Each bohrium atom has a very large nucleus, or central mass, containing positively charged particles called protons and neutral particles called neutrons. 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. The International Union of Pure and Applied Chemistry named element 107 bohrium (Bh), which was previously called unnilseptium, to honor Danish physicist and Nobel laureate Niels Bohr, who made important contributions to nuclear physics and the understanding of atomic structure.

Bohrium has the atomic number 107, which means that each bohrium atom contains 107 protons in the nucleus. Scientists have created several isotopes of bohrium, or forms of the element that contain different numbers of neutrons in the nucleus. For example, bohrium-260 contains 107 protons and 153 neutrons (107 protons + 153 neutrons = atomic mass 260). Similarly, bohrium-262 contains 107 protons and 155 neutrons.

Bohrium was first created in 1981 by researchers at the Heavy-Ion Research Laboratory in Darmstadt, Germany, by nuclear fusion of the smaller elements bismuth (Bi) and chromium (Cr). Because the bohrium nucleus contains so many particles, the atom 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).

German scientists at the Heavy-Ion Research Laboratory created bohrium-262, an isotope with a lifespan of only 0.204 seconds that is the most stable isotope of element 107. By 1998 three isotopes of bohrium were confirmed: 260, 261, and 262.

Bohrium belongs to Group 7 (VIIb) on the periodic table, which also contains the elements manganese (Mn), technetium (Tc), and rhenium (Re) (see Chemical Element). Manganese, technetium, and rhenium all form stable oxides (compounds containing oxygen), are all metallic solids with melting points above 1200° C (2192° F), and all readily dissolve in acids. 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 bohrium to share properties with other Group 7 elements. However, because of the limited amount of bohrium that can be produced and its short lifespan, scientists have been unable to determine chemical properties of this unstable element.