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What is a covalent bond?

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suhhnyd | eNotes Newbie

Posted April 28, 2013 at 11:01 PM via web

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What is a covalent bond?

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pramodpandey | College Teacher | Valedictorian

Posted May 4, 2013 at 5:52 AM (Answer #3)

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When two atom participate in chemical reaction ,one looses  electron and another gains electron to complete their outermost orbit.In this condition they form ionic bonds.

But when when  loosing and gaining of electron is not possible then they share pair of electrons  . Such sharing of electron form a covalant bonds between them.

Thus A covalent bond is a chemical bond that involves sharing a pair of electrons between atoms of two elements (Metal and Non metal,non metal and non metal ).It may be one pair,two pairs,three pairs and four pairs.

In Cl_2   one pair

 CO_2   two pairs

NH_3    three pairs

Ch_4    four pairs

Example: there's a covalent bond between the oxygen and each hydrogen in a water molecule (H2O). Each of the covalent bond contains two electrons - one from a hydrogen atom and one from the oxygen atom. Both atoms share the electrons.

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llltkl | College Teacher | Valedictorian

Posted May 5, 2013 at 4:09 PM (Answer #4)

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When atoms combine to form molecules, they tend to attain the next inert gas like electron configurations (having eight electrons, barring hydrogen which follows helium, having two electrons) in their outermost (valence) shell.  This is the famous octet rule. This gives us a good way to understand why Group I-VII elements form ions that they do, through transfer of one or more electrons. But this is not the only way of attaining octets during bond formation. While considering formation of stable homonuclear molecules like H2, Cl2 or Cn (diamond) or molecules between atoms having close values of electronegativity like CH4, NCl3 etc., there is no reason why one atom should lose an electron and an identical atom should gain it.

So, there has to be another way to attain valence shell octet. This is through sharing of electrons between atoms. Consider the formation of F2 molecule. Each fluorine atom has seven valence electrons and needs one electron to fulfil its octet. If two fluorine atoms share a pair of electrons (both atoms contributing equally towards the shared pair) in between themselves, then the stable octet configuration is achievable.  Thus one shared pair of electrons creates a single covalent bond between the two fluorine atoms. Formally, an atom can form an electron pair bond for each stable orbital. Thus hydrogen, with one stable orbital can form only a single covalent bond, viz. in HCl. The carbon atom, nitrogen atom or other second row elements are restricted to a maximum of four covalent bonds using the four orbitals in the L-shell. This is evidenced in the formation of CO2, NH4+ or CH4 – four bonds are formed in each case by sharing of four electron pairs. This restriction further emphasises the importance of octet rule in chemical bonding. Atoms of the third row onwards, however, can expand this scope through involvement of orbitals of M (and higher) shells.  

The sharing of electrons, however, occurs to as great an extent as is permitted by the number of electrons actually present. Thus, NH3, N2, BCl3 – all has three, H2O has two, Cl2 has one covalent bond within their structures.

Shared pair of electrons may originate from either the atoms, or either of them.  In the latter case, the bond is called a dative covalent (or coordinate) bond.

Often more than one covalent bond is formed between two atoms. These are called multiple bonds. Thus double or triple bonds are observed in many instances.

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user1211936 | eNoter

Posted May 3, 2013 at 4:34 AM (Answer #2)

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A covalent bond is a chemical bond that involves sharing a pair of electrons between atoms in a molecule.

Example: there's a covalent bond between the oxygen and each hydrogen in a water molecule (H2O). Each of the covalent bond contains two electrons - one from a hydrogen atom and one from the oxygen atom. Both atoms share the electrons.

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