The Covalent Bond or Molecular Bond, are chemical bonds in which there is the sharing of one or more electron pairs between atoms, with the purpose of forming stable molecules, which according to the Octet Theory :
” an atom acquires stability when it has 8 electrons in the valence shell (outermost electronic shell), or 2 electrons when it has only one shell “.
From this, unlike ionic bonds , in which the loss or gain of electrons occurs, in the covalent bonds, generally occurring between nonmetals (ametals) of the periodic table, the electronic pairs.
In other words, the name given to the electrons given by each of the nuclei of the elements, includes the sharing of atoms that seek to obtain stability. Covalent bonds are classified into: Covalent bonds and Dative covalent bonds .
Examples of Covalent Bonds
As an example of Covalent Bonding, we have the water molecule H 2 O : H – O – H , formed by two atoms of hydrogen and one of oxygen in which each trace corresponds to a shared electron pair forming a neutral molecule, since there is no loss or gain of electrons in this type of bond. Likewise, O 2 (OO) and F 2 (FF) are covalent bonds .
Dative Covalent Bond
Also called coordinated or semipolar bond, the dative covalent bond is similar to the dative bond, however it occurs when one of the atoms has its complete octet, that is, eight electrons in the last layer and the other, to complete its electronic stability, it needs to acquire two more electrons. In other words, the dative covalent bond occurs when one of the atoms shares its electrons with the other two elements.
An example of this type of bond represented by an arrow is the sulfur dioxide compound SO2: O = S → O
This is because a double bond between the sulfur and one of the oxygen is established in order to achieve its electronic stability and, in addition, sulfur donates a pair of its electrons to the other oxygen so that it has eight electrons in its valence shell. Remember that the arrow indicates that sulfur (S) is donating a pair of electrons to oxygen (O).