Nonmetals, Metalloids, and Synthetic Elements
Nonmetals
Nonmetals make up just a small portion of the elements on the periodic table,
and 11 are gases, 5 solid, and 1 is a liquid at room temperature.
Hydrogen is the simplest and smallest element but makes up about 90% of
the matter in the universe.
Nonmetals are not malleable, but are brittle. They lack luster, meaning they
are not shiny. They are nonconductors of heat and electricity, tend to gain
electron in chemical reactions, and, of course, are found on the right side of
the Periodic Table.
The more reactive nonmetals are found in group 17 . These are the halogens
(salt formers) and are too reactive to be found in pure form in nature.
• Fluorine is used in hydrofluoric acid and is used to etch glass.
Compounds of it are added to toothpaste to reduce cavities.
• Chlorine is important as a disinfectant in public pools and drinking water.
• Iodine, a solid that can sublime, is needed by the thyroid gland to make
the hormone thyroxin. An iodine salt is usually added to table salt to
prevent goiter and to make sure there is enough in our diet.
The noble gases in group 18 don’t form compounds in nature. Examples of
their use:
• Helium-balloons,lasers
• Neon-lasers,lights
• Argon-incandescant lights
• Xenon-lights
Metalloids
The metalloids or semimetals are located along the line between the metals and
nonmetals in the periodic table. The metalloids are boron, silicon, germanium,
arsenic, antimony, and tellurium. Polonium is often considered a metalloid, too.
The electronegativities and ionization energies of the metalloids are between
those of the metals and nonmetals, so the metalloids exhibit characteristics of
both classes.
Silicon, for example, possesses a metallic luster, yet it is an inefficient conductor
and is brittle. The reactivity of the metalloids depends on the element with which
they are reacting. For example, boron acts as a nonmetal when reacting with
sodium yet as a metal when reacting with fluorine. The boiling points, melting
points, and densities of the metalloids vary widely. The intermediate conductivity
of metalloids means they tend to make good semiconductors.
Summary of Common Properties of Metalloids
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Electronegativities between those of metals and nonmetals
Ionization energies between those of metals and nonmetals
Possess some characteristics of metals/some of nonmetals
Reactivity depends on properties of other elements in reaction
Often make good semiconductors
Synthetic Elements
All of the elements discovered since 1937 are not found in nature. The first
synthetic element made was Technetium, #43, so named since technology was
needed to make it.
Most of the synthetic elements have higher atomic numbers than uranium and
are called the transuranium elements. All are made by bombarding existing
elements with other atoms or atomic particles using various types of ‘atom
smashing’ machines.
The synthetic elements are unstable and break apart through the process of
radioactive decay.
Some of these synthetic elements have little practical use other than to make
other elements. Some, like plutonium for nuclear reactors and americium in
smoke detectors have found widespread use.