Double bond lewis structure and other important facts are described in this article.
Lewis structure of any molecule is the organisation of electrons among the atoms which helps to understand the bond formation. Lewis structure can be drawn for not only single bonded but also double and triple bonded compounds. To do this certain rules should be mind.
Double Bond Facts
Double bond is one kind of covalent bond where the atoms are amalgamated by two covalent bonds instead of one bond. So here four bonding electrons are found in between the joining atoms. Usually double bond can exist in among atoms of same element and unlike element.
In the case of di oxygen(O2), azo compounds(N=N), alkenes(C=C) double bonded exist in between same type of atoms. But in aldehydes(CHO), ketones(CO), imines(C=N), sulfoxides(SO2), carbon dioxide(CO2) we can understand that the atoms are united by double bonds. There are some specialities can be observed in the case of double bonded carbon compounds.
Double bonded compounds made of carbon are found to be very stronger and much smaller in its size than single bonds. Due to presence of double bonds such compounds are found to be very sensitive to reactants and acts as electron rich species. So they react with electron acceptor molecules easily.
Let’s draw the Lewis structure of one double bonded compound called carbon dioxide.
In carbon dioxide the middle carbon is joined with two oxygen atoms through double bonds. Let’s look how it is drawn. The steps dealt with are as follows
- First we need to calculate the total valence electrons present here. One carbon with two oxygen atoms has 16 valence electrons in total.
- In second step we are writing the central atom with other atoms attached into it. Usually the least electronegative atom will be taken as central atom. Here oxygen is found to be more electronegative than carbon. Since carbon has minimum electronegative character it is chosen as the central atom attached with two oxygen atoms around.
- Make only two single bonds between the atoms and then distribute the residual electrons to the atoms by fulfilling their octet rule. When two single bonds are made then there are 12 left over electrons. They are distributed oxygen first by obeying octet rule.
- The formal charge of above structure is found out and it is 2 and -1 for carbon and oxygen respectively. Carbon atom doesn’t obey octet rule too. So that structure is not correct.
- In order to decrease the formal charge, one of the non- bonding pairs of oxygen atom were involved to form bond with carbon.
- The formal charge of above structure is zero and all the atoms obey octet rule now. So this will be the correct Lewis structure for carbon dioxide.
Types of bonds in Lewis structure
There are generally three kinds of bonds are seen in Lewis structure of any molecule. There can single, double, triple bonds in between the atoms. Single bonds are made by combining atoms with two electrons or one bond. Double bonds contain atoms joined together with the help of two bonds or four electrons. Triple bonds are made with six bonding electrons among the atoms. These bonds can be constructed in between similar or dissimilar elements.
How to identify double bond in Lewis structure ?
Double bonds are involved with four bonding electrons. So when two atoms are combined together by four electrons then they made double bonds in between them.
Lewis structure double bond rules
Rule in double bond Lewis structure is same as that of Lewis structure drawing rules. They are as follows
- Calculate the sum total of valence electrons in the given molecule.
- Place least electronegative atom as central surrounded with other atoms.
- First make single bonds in between them and then the residual electrons are distributed in accordance with octet rule. Elements in period one to four obeys octet rule. Except that we try to make their outermost shell completely filled.
- If the formal charge of the compound is not zero then we have to reduce it by involving the non- bonded electrons into bond construction. This may lead to double or triple bond between the linking atoms.
Examples of Compounds with Double Bonds
Some of compounds with double bond in between the atoms are carbon dioxide, dioxygen, imines, acetone, alkenes, sulphur dioxide, azo compounds etc
Double Covalent Bond Lewis Structure
In double covalent compound there is two bonds made in between the joining atoms. Those two bonds are made by the mutual delivery of electrons between the atoms.
When and How to use double bond in Lewis structure ?
When we draw Lewis structure of any molecule, if the octet or formal charge of any atom is not satisfied then its the time to understand that the drawn structure is wrong and we have to modify it. So that is time when the double bond enters in between the atoms.
Sometimes if the valency of the atom sis not satisfied by making single bonds, then making more than bond will lead to double or triple bond formation in between the atoms. Double bonds are usually made by the involving the non bonded electrons into bond formation. Then the number of bonds increases with decrease in lone pairs around the atoms.
In this article we discussed about the Lewis structure of double bonded compounds. How and when double bond formation took place in between atoms. Lewis structure of one double bonded compound is drawn with full details.
Triple and double bonds are the common bonds seen in between the atoms instead of single bond. Double bond arrives when we understand that the Lewis structure drawn is not proper or incorrect. Examples of certain double and triple compounds are also shown here in this article.