In 1996, only a little more than a year after they created
element 111, a team of German scientists led by Peter Armbruster at the
Gesellschaft für schwerionenforschung (GSI) facility at Darmstadt, Germany,
claimed to have created an atom of the element 112. Its nucleus has 112 protons
and 166 neutrons, giving it a mass number of 277. As a new element it was named
ununbium, symbol Uub, according to an internationally adopted system for naming
new elements. This was based on the presence of one atom of the element made by
accelerating zinc atoms to high speed and bombarding them into lead. When an
atom of each fused to make the new nucleus, it lasted a fraction of a
thousandth of a second before decaying, emitting an alpha particle to become a
nucleus of element 110.
What is an element?
A chemical element or element is a species of atoms having
the same number of protons in their atomic nuclei (i.e. the same atomic number,
Z). There are 118 elements that have been identified, of which the first 94
occur naturally on Earth with the remaining 24 being synthetic elements. There
are 80 elements that have at least one stable isotope and 38 that have
exclusively radioactive isotopes, which decay over time into other elements.
Iron is the most abundant element (by mass) making up the Earth, while oxygen
is the most common element in the crust of the earth.
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| The Periodic Table, by Sandbh (Own work) via Wikimedia Commons |
Chemical elements constitute all of the ordinary matter of
the universe. However astronomical observations suggest that ordinary
observable matter is only approximately 15% of the matter in the universe: the
remainder is dark matter, the composition of which is unknown, but it is not
composed of chemical elements. The two lightest elements, hydrogen and helium
were mostly formed in the Big Bang and are the most common elements in the
universe. The next three elements (lithium, beryllium and boron) were formed
mostly by cosmic ray spallation, and are thus more rare than those that follow.
Formation of elements with from six to twenty six protons occurred and
continues to occur in main sequence stars via stellar nucleosynthesis. The high
abundance of oxygen, silicon, and iron on Earth reflects their common
production in such stars. Elements with greater than twenty-six protons are
formed by supernova nucleosynthesis in supernovae, which, when they explode,
blast these elements far into space as planetary nebulae, where they may become
incorporated into planets when they are formed.
The term "element" is used for a kind of atom
with a given number of protons (regardless of whether they are or they are not
ionized or chemically bonded, e.g. hydrogen in water) as well as for a pure
chemical substance consisting of a single element (e.g. hydrogen gas).
When different elements are chemically combined, with the
atoms held together by chemical bonds, they form chemical compounds. Only a
minority of elements are found uncombined as relatively pure minerals. Among
the more common of such "native elements" are copper, silver, gold,
carbon (as coal, graphite, or diamonds), and sulphur. All but a few of the most
inert elements, such as noble gases and noble metals, are usually found on
Earth in chemically combined form, as chemical compounds. While about 32 of the
chemical elements occur on Earth in native uncombined forms, most of these
occur as mixtures. For example, atmospheric air is primarily a mixture of
nitrogen, oxygen, and argon, and native solid elements occur in alloys, such as
that of iron and nickel.
The history of the discovery and use of the elements began
with primitive human societies that found native elements like carbon, sulphur,
copper and gold. Later civilizations extracted elemental copper, tin, lead and
iron from their ores by smelting, using charcoal. Alchemists and chemists
subsequently identified many more, with almost all of the naturally-occurring
elements becoming known by 1900.
The properties of the chemical elements are summarized on
the periodic table, which organizes the elements by increasing atomic number
into rows ("periods") in which the columns ("groups") share
recurring ("periodic") physical and chemical properties. Save for
unstable radioactive elements with short half-lives, all of the elements are
available industrially, most of them in high degrees of purity.
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