Chemical Bonds: Ionic and Covalent

Chemical Bonds: Ionic and Covalent Bonding A chemical bond is an attraction between atoms that lets chemical substances that contain two or more atoms. Two forms of chemical bonding are ionic bonding and covalent bonding. Additionally, ionic and covalent bonds can be combined to form mixtures and compounds. Ionic and covalent bonds are formed through the bonding of two or more elements. An element is a pure substance composed of a single atom. There are currently 117 known elements with 94 elements occurring naturally and 22 artificial elements.

The properties and names of all known elements can be found on the Periodic Table. Ionic bonded and covalent bonded substances can be combined to create either a mixture or a compound. A mixture is a heterogeneous form of matter that is composed of variable proportions of molecules and atoms. The properties of a mixture include the variability of the composition that means that a mixture can be any combination of substances.

In a mixture, the components that make up that mixture retain their individual characteristic properties and the components of said mixture are easily separated. Mixtures can be separated through various forms including dialysis, chromatography, and electrophoresis. In biochemistry, dialysis is the separation of molecules in a solution based on their differing rates of diffusion through a semi-permeable membrane. Chromatography is a separation method that is based on the differences in the partitioning behavior between a mobile phase and a stationary phase.

Electrophoresis is the separation of substances based on the rate of movement of each component in a colloidal suspension when under the influence of an electric field. Compounds are pure substances that are composed of two or more elements. Unlike a mixture, a compound is a homogeneous form a matter in which the elements are present in fixed proportions. Additionally, components that comprise a compound do not retain their individual properties and large inputs of energy are required to separate a compound into its separate components.

Compounds are formed naturally to provide elemental stability; stability is determined by the number of electrons present in the outermost energy level of an atom. Ionic bonds are formed when atoms link together due to the attraction of ions with opposing charges. In ionic bonding, electrons are completely transferred from one of the bonding atoms to another atom. These electrons are attracted to each other through electrostatic forces. When one atom gives up or loses an electron, the atom will reduce in size.

When an atom gains or receives an electron, the atom will grow in size. Ionic bonds lead to the formation of crystalline solids with high melting points and can be dissolved in water and other polar solvents. The ionic compounds formed through bonding are always solid and are good conductors of electricity. Ionic bonds are formed when a metallic element on the Periodic Table donates one or more electrons and forms a positive ion, or cation, and has a stable electron configuration.

These positive ions enter a non-metallic element causing it to form a negative electron, or anion that has a stable electron configuration. Electrostatic forces attract cations and anions to each other. Ionic compounds include NaCl, or sodium chloride commonly known as table salt, and MgO, also known as magnesium oxide. Covalent bonds do not give up electrons, but rather share electrons equally. Covalent bonding occurs because the atoms in a compound have a similar ability to gain and lose ions.

Unlike ionic bonds that form between a metal and a non-metal, covalent bonds form between non-metals. Covalent bonding requires that molecules exist in their true form; covalent molecules are not attracted to each other through electrostatic forces and exist freely in liquids.