A Lewis structure is a picture of a molecule that shows the covalent bonds and pairs of free electrons.The octet rule is the basis for Lewis structures. Lewis structures are useful for describing chemical bonds but have some flaws. For example, they don’t account for aromaticity, and they don’t give a good picture of how something behaves magnetically. Let us study Lewis dot structures in detail.
Lewis Dot Structures
What is Lewis Electron Dot Structure?
A Lewis structure is a way to show the shape of a molecule. Dots show where electrons are around the atoms, and lines or pairs of dots show where covalent bonds connect the atoms. By drawing a Lewis dot structure, you can find the lone electron pairs in molecules, which helps you figure out how chemical bonds form.
Molecules with covalent bonds and compounds held together by ions can have Lewis structures. Covalent bonds work because electrons are shared. In an ionic bond, one atom gives the other one of its electrons. Lewis structures are named after Gilbert N. Lewis, who wrote an article called “The Atom and the Molecule” in 1916 in which he first talked about the idea.
How to Draw Lewis Electron Dot Structures?
I. Find out how many valence electrons each atom in the molecule has. Each carbon has four valence electrons, just like carbon dioxide. Oxygen has six valence electrons.
II. If a molecule has more than one type of atom, the one with the most metal or the least negative charge goes in the middle. If you don’t know the electronegativity, remember that as you move away from fluorine on the periodic table, electronegativity tends to go down.
III. Set up the electrons so that each atom contributes one electron to each bond.
IV. Count how many electrons are around each atom. If each has eight, or an octet, then the octet is finished. If it doesn’t, go to the next step.
If an atom is missing dots, redraw the structure so that some electrons form pairs. This will bring the number of dots on each atom up to eight. For example, in the first structure of carbon dioxide, each oxygen atom has seven electrons and each carbon atom has six electrons. The final structure has two pairs (two sets of two dots) on each oxygen atom, two oxygen electron dots facing the carbon atom, and two sets of carbon dots (two electrons on each side). Between each oxygen and carbon, there are four electrons, which are shown as double bonds.
Formal Charge Formula
When you write Lewis structures, you should put formal charges next to each atom that has a formal charge that isn’t 0. (Usually, the charge is circled to make it clear.) This can also help you pick out the good Lewis structures. Most of the time, atoms that pull electrons strongly should have negative formal charges (like O or F, elements from the top right of the periodic table that have high ionization energies and high electron affinities).
Elements that pull electrons less should have positive formal charges. Most of the time, formal charges that are more than two are bad. And it’s better to have formal charges that are the opposite of each other next to each other (so you get an “ionic bond”) than to have formal charges that are the same as each other close together.
Lewis Structure Examples
Lewis Structure of CO2
In the Lewis structure of CO2, there are two double bonds between the carbon and oxygen atoms. The octet rule says that each oxygen atom needs to bond with four different carbon atoms. Carbon has four valence electrons, which make a total of four bonds. So there are four dots around carbon. Oxygen only needs two bonds, which are shown by the single dots to the left and right of the O. The dots above and below the Os won’t stick together.
First, put the carbon in the middle of the CO2 Lewis structure. Connect both O atoms to C. There will not be any direct ties between the O’s. Carbon is always in the middle, and the other atoms are connected to it. Second, connect each O’s single dot to the C in the middle. Each O must connect twice. And four bonds are needed for carbon. So it makes sense that C bonds twice with each O.
Lewis Structure of O2
The two parallel lines between the O atoms show where the two bonds are. We call this a “double bond.” Each bond is made up of two electrons, one from each of the O atoms that are connected. So, the two parallel lines that make up the double bond stand for a total of 4 electrons. Each O is surrounded by four dots and two lines, which stand for four more electrons in the double bond between the O2 molecules. So, each O is surrounded by a total of 8 valence electrons, making it stable with an octet.
In the O2 Lewis structure, the centers of the oxygen atoms are shown by the two letter O’s. The nuclei are the solid parts of the molecule. They are made up of protons and neutrons. Electrons, which are not solid, are shown by the dots and lines, which is interesting. The diagram is way out of proportion because the nucleus is usually about the size of a pea in a stadium compared to the electrons around it.
- Lewis Structure of CO
CO has a Lewis Structure that looks like three straight lines between the C and O atoms and two dots on each atom. Because the atoms of Carbon and Oxygen form a triple bond, which we talked about above. Why does each atom have two dots? These dots represent valence electrons. Carbon monoxide has a unique Lewis structure because there are three bonds between the C and O atoms. To fill their valence shells, these atoms form a triple bond.
Solved Examples
Example 1: Draw the lewis structure of nitrogen dioxide?
Solution: Because of the way nitrogen dioxideelectrons are set up, nitrogen dioxide does not have a single Lewis structure. The double bond moves around over time, so either of the oxygen atoms could have a double bond with the nitrogen atom at any time. In this way, the resonance Lewis structure is a way to describe nitrogen dioxide. Nitrogen dioxide needs a resonance Lewis structure because the arrangement of its electrons keeps switching between two different forms.
FAQs on Lewis Dot Structures
Question 1. What are Lewis structures used for?
Answer. Lewis structures are meant to give chemists a simple way to look at molecules that lets them make accurate predictions about the actual molecules’ structure and properties.
Question 2. Why is it important to have Lewis structures?
Answer. Lewis structures are very important for figuring out the shape, polarity, and reactivity of (in)organic compounds. For each atom, the Lewis structure is made by putting a dot around the atom for each valence electron it has.
