In
chemistry
Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions ...
, the term chemically inert is used to describe a substance that is not
chemically reactive
In chemistry, reactivity is the impulse for which a chemical substance undergoes a chemical reaction, either by itself or with other materials, with an overall release of energy.
''Reactivity'' refers to:
* the chemical reactions of a single sub ...
. From a thermodynamic perspective, a substance is inert, or
nonlabile, if it is thermodynamically
unstable (positive
standard Gibbs free energy of formation
The standard Gibbs free energy of formation (''G''f°) of a compound is the change of Gibbs free energy that accompanies the formation of 1 mole of a substance in its standard state from its constituent elements in their standard states (the most s ...
) yet decomposes at a slow, or negligible rate.
Most of the
noble gases, which appear in the last column of the
periodic table
The periodic table, also known as the periodic table of the (chemical) elements, is a rows and columns arrangement of the chemical elements. It is widely used in chemistry, physics, and other sciences, and is generally seen as an icon of ch ...
, are classified as inert (or unreactive). These elements are stable in their naturally occurring form (gaseous form) and they are called
inert gases.
Noble gas
The noble gases (
helium,
neon
Neon is a chemical element with the symbol Ne and atomic number 10. It is a noble gas. Neon is a colorless, odorless, inert monatomic gas under standard conditions, with about two-thirds the density of air. It was discovered (along with krypton ...
,
argon,
krypton,
xenon and
radon) were previously known as 'inert gases' because of their perceived lack of participation in any chemical reactions. The reason for this is that their outermost
electron shells (valence shells) are completely filled, so that they have little tendency to gain or lose electrons. They are said to acquire a
noble gas configuration
In atomic physics and quantum chemistry, the electron configuration is the distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals. For example, the electron configuration of the neon a ...
, or a full
electron configuration
In atomic physics and quantum chemistry, the electron configuration is the distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals. For example, the electron configuration of the neon atom ...
.
It is now known that most of these gases in fact ''do'' react to form
chemical compounds, such as
xenon tetrafluoride. Hence, they have been renamed to 'noble gases', as the only two of these we know truly to be inert are helium and neon. However, a large amount of energy is required to drive such reactions, usually in the form of heat, pressure, or radiation, often assisted by
catalysts. The resulting compounds often need to be kept in moisture-free conditions at low temperatures to prevent rapid decomposition back into their elements.
Inert gas
The term ''inert'' may also be applied in a relative sense. For example, molecular
nitrogen is an
inert gas under ordinary conditions, existing as
diatomic molecules, . The presence of a strong triple
covalent bond
A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atoms ...
in the molecule renders it unreactive under normal circumstances. Nevertheless, nitrogen gas does react with the
alkali metal
The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K),The symbols Na and K for sodium and potassium are derived from their Latin names, ''natrium'' and ''kalium''; these are still the origins of the names ...
lithium to form compound
lithium nitride (Li
3N), even under ordinary conditions. Under high pressures and temperatures and with the right catalysts, nitrogen becomes more reactive; the
Haber process uses such conditions to produce
ammonia from atmospheric nitrogen.
Main uses
Inert atmospheres consisting of gases such as
argon,
nitrogen, or
helium are commonly used in chemical reaction chambers and in storage containers for
oxygen- or
water-sensitive substances, to prevent unwanted reactions of these substances with oxygen or water.
Argon is widely used in
fluorescence tubes and low energy light bulbs. Argon gas helps to protect the metal filament inside the bulb from reacting with oxygen and
corroding
Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engi ...
the filament under high temperature.
Neon
Neon is a chemical element with the symbol Ne and atomic number 10. It is a noble gas. Neon is a colorless, odorless, inert monatomic gas under standard conditions, with about two-thirds the density of air. It was discovered (along with krypton ...
is used in making advertising signs. Neon gas in a vacuum tube glows bright red in colour when electricity is passed through. Different coloured neon lights can also be made by using other gases.
Helium gas is mainly used to fill hot air and party balloons. Balloons filled with it float upwards and this phenomenon is achieved as helium gas is less dense than air.
See also
*
Noble metal
References
{{Reflist
Chemical nomenclature
Chemical properties
Gases
Industrial gases
Noble gases