Ionic Bonding

The first explanation of chemical bonding was suggested by the properties of salts. Salts are generally crystalline solids that melt at high temperature. Sodium chloride for example, the white crystalline melt at 801^oC. The liquid after melting (molten) salt conduct an electric current. And a salt dissolved in water gives a solution that also conducts and electric current. The electric conductivity of the molten salt and the salt solution is resulted from the motion of ions in the liquid. A salt is formed between two atoms hold by ionic bonding. An ionic bonding corresponds to electrostatic attraction between positive and negative ions. It form between two atoms when one or more electrons are transferred from the valence shell of one atom to the valence shell of the other. The atom that loses electrons becomes positive ion (cation) and the atom that gains electrons becomes negative ion (anion). Any given ion tend to attract as many neighboring ions of opposite charge as possible. When the large number of ion gather together, they form an ionic solid. The losing and gaining electron of the atom cause the electron configuration changing.

The trend of electron configuration changing

The unstable elements tend to reach similar electron configuration with nearly noble gas by electron configuration changing. There are two trends, first the element atom trend to remove valence electrons , and secondly the element atom trend to gain valence electrons.

If the atom of an element removes it’s valence electron the positive charge particle occurs due to differences or proton and electron number in it. The number of electron will decrease and less then the number or proton, so that he atom change to the positive charge particle. We say the elements is electropositive elements.

In the opposite trends, if an atom gains valence electron, the number of electron increase and more than the number of proton, so that the atom change to the negative charge particle. The elements with trends to gain electron is named electronegative elements.

Example 1.1 :

Lithium has atomic number 3. It has electron configuration 2 1. It’s valence electron is 1 so lithium is unstable. To reach stability it must change to duplet system like helium by remove a valence electron and form lithium ion .

Li : 2 1 remove 1 valence electron to be Li ion (Li⁺) : 2

The lithium ion more stable than lithium atom

Example 1.2:

Magnesium has atomic number 12. The electron configuration is 2 8 1. It’s valence electron is 2 so it must change to octet system like neon with 2 8 electron configuration. Magnesium atom must remove two valence electron and form magnesium ion with (2+) number of charge.

Mg : 2 8 2 remove 2 valence electron to be Mg ion (Mg²⁺) : 2 8

Examples 1.3 :

Fluorine atom has atomic number 9. It’s electron configuration is 2 7. It need an electron to reach octet system. If fluorine atom gain an electron will form fluoride ion (F^-) that has 2 8 electron configuration like neon. So that fluoride ion more stable than fluorine atom.

F : 2 7 gain 1 valence electron to be fluoride ion (F^-) : 2 8

The ionic compound that formed between lithium and fluorine is LiF. Lithium loses an electron and fluorine gains it. The Li⁺ and F^- are formed and the attract to form neutral LiF compound. But if the compound is formed between magnesium and fluorine, the magnesium will removes two electrons, so in this case the two fluorine atoms are needed to gain two electrons. The formula of compound formed is MgF₂.