Thursday, 6 March 2014

UNDERSTANDING CHEMISTRY

Formation of Covalent Bond
A covalent bond is formed when the atoms of same or different elements combine by mutual sharing of electrons. Covalent compounds are formed only by the interactions of non-metal atoms. The number of atoms which make up covalent molecules is determined by the number of electrons in outer levels and the Octet Rule.

  
HYDROGEN: Forms single Covalent Bond
The simplest covalent molecule is the diatomic hydrogen molecule.
The "octet" for hydrogen is only 2 electrons since the nearest noble gas is He. The diatomic molecule is formed because individual hydrogen atoms containing only a single electron are unstable. The covalent bond holds the two atoms together because the pair of electrons is attracted to both nuclei.


 OXYGEN: Forms double Covalent Bond
Oxygen has six valence electrons  , hence short of two electrons to attain the stability of nearest noble gas Ne.
To attain stability double covalent bond is formed by sharing of four electrons between two oxygen atoms.

 



 NITROGEN: Forms triple Covalent Bond

Nitrogen has five valence electrons , hence short of three electrons to attain the stability of nearest noble gas Ne.
To attain stability triple covalent bond is formed by sharing of four electrons between two oxygen atoms.




Conditions necessary for the formation of covalent bonds:
·         A bond formed by mutual sharing of electrons
·         Formed between two or more non-metals – difference in electro negativity should not be high.
·         A single bond represents 2 electrons
·         They satisfy the octet rule by sharing of electrons
·         These molecules have a definite shape


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