A dianion is an
anion
An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...
with a net charge of −2. While there exist many stable molecular dianions, such as and , thus far no stable atomic dianion has been found:
Electron shielding and other quantum mechanical effects tend to make the addition of another electron to an atomic anion unstable.
The most heavily studied atomic dianion is H, usually as a short-lived
resonance
Resonance is a phenomenon that occurs when an object or system is subjected to an external force or vibration whose frequency matches a resonant frequency (or resonance frequency) of the system, defined as a frequency that generates a maximu ...
between an
electron
The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...
and a
hydrogen ion
A hydrogen ion is created when a hydrogen atom loses or gains an electron. A positively charged hydrogen ion (or proton) can readily combine with other particles and therefore is only seen isolated when it is in a gaseous state or a nearly particl ...
.
In 1976, its half-life was experimentally measured to be 23 ± 4 nanoseconds.
In the field of
physiology
Physiology (; ) is the science, scientific study of function (biology), functions and mechanism (biology), mechanisms in a life, living system. As a branches of science, subdiscipline of biology, physiology focuses on how organisms, organ syst ...
, molecular dianions play an important roles, such as the monohydrogen phosphate (), present at a concentration of around 1 mM in the blood and in cells, where it plays a role in pH buffering.
See also
*
Dication
References
Anions
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