Chemical Bond

Chemical bond is an attraction that hold atoms together forming molecule and formula unit.  There are three general types of bonds: the ionic, covalent and metallic.

Ionic bond refers to electrostatic attraction between ions of opposite charge, the cation and anion forming ionic compound.  The bond is formed by transfer of electrons from metal to nonmetal.  Further discussion about this on my next post.

Covalent bond is another type of bond which involve sharing of valence electrons between two nonmetals.  The best example is the sharing of electrons of diatomic molecules like H₂, O₂, etc. Detailed discussion on my next post.

Metallic bond on the other hand is a bond that exist in metals such as aluminum, copper, and iron. In metals each atom is bonded to several neighboring atoms.  The valence electrons in metallic bonding forms sea of valence electrons that are free to move throughout the three-dimensional structure of the metal.

Lewis Symbol

In chemical bonding, the one responsible are the valence electrons, the electrons occupying the highest energy level of an atom.  We also learn that the valence electrons of representative elements are the same with the group number of the elements.  

Now to easily understand covalent bonding, we need to learn how to write Lewis Symbol.  Lewis symbol for an element consist of the chemical symbol for the element plus dots representing the valence electrons surrounding the chemical symbol.  This Lewis symbol was formulated by an American Chemist G.N. Lewis (1875 - 1946) and now known as the Lewis electron-dot symbols or merely Lewis symbol. 

Below are the Lewis symbol of Representative elements:

The Octet Rule

Why atoms undergo reaction?  Do they want something?  Yes, atoms want to become stable.  Just like us we do something to our life to become stable financially, emotionally and more.  Atoms became stable either by giving up, accepting or sharing their valence electrons.  But atoms follow a certain rule to achieve stability.  And what is that rule,  and that's the Octet Rule.  Octet Rule states that atoms gain stability by achieving 8 valence electrons same with the noble gases.  

 Exception of the Octet Rule

There are many exceptions to the Octet Rule, one of this are the elements consisting of less than 4 valence electrons located in the first and second period, will not complete the 8 valence electrons such as H, Li and B.  There are also some elements that can have more that 8 valence electrons, those elements containing 5 or more valence electrons.