Covalent Bonding
Covalent bonding is a form of chemical bonding characterized by the sharing of one or more pairs of electrons, by two atoms, in order to produce a mutual attraction. The atoms tend to share electrons, so as to fill their outer electron shells. Such bonds are always stronger than the intermolecular hydrogen bond and similar in strength or stronger than the ionic bond. Commonly a covalent bond implies the sharing of just a single pair of electrons. The sharing of two pairs of electrons is called a double bond and three pairs are called a triple bond. The triple bond is relatively rare in nature, and two atoms are not observed to bond more than triply. A covalent bond is typically formed by two non-metals. Non-metals have similar electronegativities. Consequently, neither atom is strong enough to steal electrons from the other. Therefore, the atoms must share the electrons. In short, a covalent bond exists when two or more electrons (in pairs) are shared by two non-metallic atoms. Each atom donates half of the electrons to be shared. This sharing of electrons is a result of the electronegativity (electron attracting ability) of the two bonded atoms which is either equal to or no greater than 1.7. If the electronegativity difference is greater than 1.7 then the higher electronegative atom has an electron attracting ability large enough to force the transfer of electrons from the less electronegative atom. This would be an ionic bond. As long as the electronegativity difference is no greater than 1.7 the atoms can only share the bonding electrons. Two atoms with the same electronegativity will share the bonding electron pairs equally. As a result the bonding electrons will be evenly distributed between the bonded atoms. There will be no accumulation of bonding electrons on any one atom. Covalent bonding also most frequently occurs between atoms with similar electronegativities because neither atom can provide sufficient energy to completely...
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