In almost all cases, chemistry bonds are created by interactions of valence electrons in atoms. To facilitate our expertise of exactly how valence electron interact, a simple means of representing those valence electrons would certainly be useful.

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A Lewis electron dot diagramA representation of the valence electrons of one atom that offers dots approximately the prize of the element. (or electron dot diagram or a Lewis chart or a Lewis structure) is a depiction of the valence electron of one atom that provides dots approximately the symbol of the element. The number of dots amounts to the variety of valence electrons in the atom. These dots are arranged come the right and left and over and below the symbol, v no an ext than 2 dots ~ above a side. (It go not matter what stimulate the positions are used.) for example, the Lewis electron dot diagram because that hydrogen is simply


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By placing the two electrons with each other on the very same side, us emphasize the truth that these 2 electrons room both in the 1s subshell; this is the typical convention we will certainly adopt, return there will be exception later. The following atom, lithium, has an electron configuration of 1s22s1, therefore it has only one electron in that valence shell. That electron dot diagram resembles that of hydrogen, other than the symbol because that lithium is used:


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Beryllium has two valence electrons in its 2s shell, for this reason its electron dot diagram is favor that the helium:


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The next atom is boron. That valence electron shell is 2s22p1, for this reason it has three valence electrons. The third electron will go on another side of the symbol:


Again, that does not matter on which sides of the symbol the electron dots space positioned.

For carbon, over there are four valence electrons, two in the 2s subshell and also two in the 2p subshell. As usual, us will attract two dots with each other on one side, to represent the 2s electrons. However, conventionally, we attract the dots because that the two p electrons on different sides. As such, the electron dot diagram for carbon is together follows:


For oxygen, i m sorry has four p electrons, we now need to start copy up ~ above the dots top top one various other side of the symbol. As soon as doubling up electrons, make certain that a side has actually no an ext than two electrons.


With the following element, sodium, the process starts over with a single electron due to the fact that sodium has a solitary electron in that is highest-numbered shell, the n = 3 shell. By going through the regular table, we view that the Lewis electron dot diagrams of atoms will never have an ext than eight dots approximately the atom symbol.


Example 1

What is the Lewis electron period diagram for each element?

aluminum selenium

Solution

The valence electron configuration for aluminum is 3s23p1. So that would have actually three dots roughly the symbol because that aluminum, two of them paired to stand for the 3s electrons:


The valence electron construction for selenium is 4s24p4. In the highest-numbered shell, the n = 4 shell, over there are six electrons. The electron period diagram is as follows:


For atom with partially filled d or f subshells, these electrons are frequently omitted indigenous Lewis electron dot diagrams. Because that example, the electron dot diagram for iron (valence covering configuration 4s23d6) is together follows:


Elements in the same column of the routine table have similar Lewis electron period diagrams because they have actually the very same valence covering electron configuration. Therefore the electron period diagrams for the first column of elements are as follows:


Monatomic ions space atoms that have actually either shed (for cations) or acquired (for anions) electrons. Electron period diagrams for ions are the same as for atoms, except that part electrons have actually been eliminated for cations, while some electrons have been included for anions. Hence in to compare the electron configurations and electron period diagrams for the Na atom and also the Na+ ion, we note that the Na atom has a single valence electron in that Lewis diagram, if the Na+ ion has lost that one valence electron:


Technically, the valence shell of the Na+ ion is currently the n = 2 shell, which has actually eight electrons in it. So why do we not put eight dots approximately Na+? Conventionally, as soon as we present electron period diagrams because that ions, we show the original valence shell of the atom, i m sorry in this case is the n = 3 shell and also empty in the Na+ ion.

In do cations, electron are first lost indigenous the highest numbered shell, no necessarily the critical subshell filled. For example, in going indigenous the neutral Fe atom to the Fe2+ ion, the Fe atom loser its two 4s electrons first, no its 3d electrons, regardless of the fact that the 3d subshell is the last subshell being filled. Therefore we have


Anions have extra electrons when contrasted to the original atom. Right here is a to compare of the Cl atom v the Cl− ion:


Example 2

What is the Lewis electron period diagram for each ion?

Ca2+ O2−

Solution

Having shed its two original valence electrons, the Lewis electron dot diagram is simply Ca2+.

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Ca2+

The O2− ion has acquired two electrons in that is valence shell, therefore its Lewis electron dot diagram is as follows:


Test Yourself

The valence electron configuration of thallium, who symbol is Tl, is 6s25d106p1. What is the Lewis electron dot diagram for the Tl+ ion?

Answer


Key Takeaways

Lewis electron dot diagrams use dots to represent valence electrons roughly an atomic symbol. Lewis electron period diagrams for ions have actually less (for cations) or more (for anions) dots 보다 the corresponding atom.

Explain why the an initial two dots in a Lewis electron dot diagram are attracted on the same side the the atomic symbol.


Is it necessary for the an initial dot about an atom symbol to walk on a specific side that the atom symbol?