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In an ionic bond, one atom loses an electron to another
atom, forming a cation and anion, respectively. And, as everyone knows,
opposites attract.
An IONIC BOND is an electrostatic interaction that holds jointly
a positively charged ion (cation) and a negatively charged ion (anion).
In table salt, for example, a valence electron from a sodium
atom is transferred to a chlorine atom, forming Na+ and Cl-. As the ions have
opposite charges, they are attracted to each other. The loss of a valence
electron and the attraction to the atom that took it happen at the same time.
It is possible for more than one valence electron to be
drawn away from another atom, as in barium chloride (BaCl2, a substance used in
medicinal preparations). In barium chloride, two chlorine atoms each take one valence
electron away from barium, leaving the barium ion Ba2+.
Different water or oxygen, which have covalent bonds,
substances that have ionic bonds do not exist logically as discrete molecules.
Rather, they form IONIC SOLIDS, three-dimensional networks in which each cation
is bounded by anions and each anion is surrounded by cations.
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Where are ionic bonds found? These types of bonds usually
form while metal atoms bond with nonmetal atoms. In salt, the metal sodium
bonds with the nonmetal chlorine. Besides salt, some other examples are lithium
fluoride (LiF), strontium oxide (SrO) and calcium chloride (CaCl2).
Notice that when sodium loses its one valence electron it
gets lesser in size, at the same time as chlorine grows larger when it gains an
additional valence electron. This is typical of the relative sizes of ions to
atoms. Positive ions tend to be smaller than their parent atoms while negative
ions tend to be superior than their parent. After the reaction takes place, the
charged Na+ and Cl- ions are held together by electrostatic forces, thus
forming an ionic bond. Ionic compounds share many features in ordinary:
- In naming simple ionic compounds, the metal is always first, the nonmetal second (e.g., sodium chloride).
- In solution, ionic compounds easily conduct electricity.
- Ionic bonds form between metals and nonmetals.
- Ionic compounds dissolve easily in water and other polar solvents.
- Ionic compounds tend to form crystalline solids with high melting temperatures.
This last feature, the fact that ionic compounds are solids,
results from the intermolecular forces (forces between molecules) in ionic
solids. If we consider a solid crystal of sodium chloride, the solid is made up
of many positively charged sodium ions (pictured less than small gray spheres)
and an equal number of negatively charged chlorine ions (green spheres). Due to
the interaction of the charged ions, the sodium and chlorine ions are arranged
in an alternating fashion as demonstrated in the schematic. Each sodium ion is
attracted equally to all of its neighboring chlorine ions, and likewise for the
chlorine to sodium attraction. The concept of a single molecule does not apply
to ionic crystals because the solid exists as one continuous system. Ionic
solids form crystals with high melting points because of the physically
powerful forces between neighboring ions.
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