Binary
acids
An acid is a molecule or ion capable of either donating a proton (i.e. hydrogen cation, H+), known as a Brønsted–Lowry acid, or forming a covalent bond with an electron pair, known as a Lewis acid.
The first category of acids are the ...
or hydracids are certain molecular compounds in which
hydrogen
Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...
is bonded with one other
nonmetal
In the context of the periodic table, a nonmetal is a chemical element that mostly lacks distinctive metallic properties. They range from colorless gases like hydrogen to shiny crystals like iodine. Physically, they are usually lighter (less ...
lic
element.
This distinguishes them from other types of acids with more than two constituent elements. The "binary" nature of binary acids is not determined by the number of atoms in a molecule, but rather how many elements it contains. For example, hydrosulfuric acid is cited as a binary acid, even though its formula is H
2S.
Examples of binary acids:
*
HF
*
H2S
*
HCl
*
HBr
*
HI
*
HAt
A hat is a Headgear, head covering which is worn for various reasons, including protection against weather conditions, ceremonial reasons such as university graduation, religious reasons, safety, or as a fashion accessory. Hats which incorpor ...
*
For a given binary acid where element X is bonded to H, its strength depends on the
solvation
Solvations describes the interaction of a solvent with dissolved molecules. Both ionized and uncharged molecules interact strongly with a solvent, and the strength and nature of this interaction influence many properties of the solute, includi ...
of the initial acid, the
bond energy
In chemistry, bond energy (''BE'') is one measure of the strength of a chemical bond. It is sometimes called the mean bond, bond enthalpy, average bond enthalpy, or bond strength. IUPAC defines bond energy as the average value of the gas-phase b ...
between H and X,
the
electron affinity
The electron affinity (''E''ea) of an atom or molecule is defined as the amount of energy released when an electron attaches to a neutral atom or molecule in the gaseous state to form an anion.
::X(g) + e− → X−(g) + energy
This differs by si ...
energy of X, and the solvation energy of X. Observed trends in acidity correlate with bond energies, the weaker the H-X bond, the stronger the acid. For example, there is a weak bond between hydrogen and
iodine
Iodine is a chemical element; it has symbol I and atomic number 53. The heaviest of the stable halogens, it exists at standard conditions as a semi-lustrous, non-metallic solid that melts to form a deep violet liquid at , and boils to a vi ...
in
hydroiodic acid, making it a very
strong acid
Acid strength is the tendency of an acid, symbolised by the chemical formula , to dissociate into a hydron (chemistry), proton, , and an anion, . The Dissociation (chemistry), dissociation or ionization of a strong acid in solution is effectivel ...
.
In the simplest case, binary acid names are formed by combining the prefix ''hydro-'', the name of the non-hydrogen nonmetallic element, the suffix ''-ic'', and adding ''acid'' as a second word.
However, there are exceptions to this rule, e.g.
hydrazoic acid,
Binary acids are often contrasted with oxyacids, which are acids that contain oxygen and other compounds. However, other categories of acids remain in widespread use, including
carboxylic acid
In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an Substituent, R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl ...
s. In addition, there are subcategories of binary acids, such as
hydrohalic acids, which are binary acids where X is one of the
halogen
The halogens () are a group in the periodic table consisting of six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and the radioactive elements astatine (At) and tennessine (Ts), though some authors would ...
s.
See also
*
Acid
An acid is a molecule or ion capable of either donating a proton (i.e. Hydron, hydrogen cation, H+), known as a Brønsted–Lowry acid–base theory, Brønsted–Lowry acid, or forming a covalent bond with an electron pair, known as a Lewis ...
*
Oxyacid
An oxyacid, oxoacid, or ternary acid is an acid that contains oxygen. Specifically, it is a compound that contains hydrogen, oxygen, and at least one other element, with at least one hydrogen atom bonded to oxygen that can dissociate to produce ...
References
*Hill; Petrucci; McCreary; Perry. General Chemistry, Fourth Edition. New Jersey, Pearson Prentice Hall. 2005
Acids
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