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

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A Lewis electron period diagramA depiction of the valence electrons of an atom that uses dots about the prize of the element. (or electron dot diagram or a Lewis diagram or a Lewis structure) is a representation of the valence electron of an atom that offers dots around the prize of the element. The variety of dots equates to the variety of valence electron in the atom. These dots room arranged come the right and also left and over and below the symbol, v no an ext than 2 dots top top a side. (It walk not matter what bespeak the positions space used.) for example, the Lewis electron dot diagram because that hydrogen is simply




By placing the two electrons together on the exact same side, we emphasize the truth that these 2 electrons are both in the 1s subshell; this is the usual convention we will certainly adopt, although there will certainly be exceptions later. The next atom, lithium, has an electron construction of 1s22s1, for this reason it has actually only one electron in the valence shell. That electron dot diagram resembles the of hydrogen, except the symbol for lithium is used:


Beryllium has actually two valence electron in the 2s shell, for this reason its electron period diagram is choose that the helium:


The following atom is boron. Its valence electron shell is 2s22p1, so it has actually three valence electrons. The third electron will go on an additional side of the symbol:

Again, it does not matter on which political parties of the prize the electron dots are positioned.

For carbon, over there are 4 valence electrons, 2 in the 2s subshell and two in the 2p subshell. As usual, us will attract two dots together on one side, to represent the 2s electrons. However, conventionally, we draw the dots because that the 2 p electrons on different sides. As such, the electron period diagram for carbon is together follows:

For oxygen, i beg your pardon has four p electrons, us now need to start copy up top top the dots ~ above one other side that the symbol. When doubling increase electrons, make sure that a side has no more than 2 electrons.

With the next element, sodium, the process starts over through a single electron due to the fact that sodium has actually a solitary electron in that highest-numbered shell, the n = 3 shell. Through going through the periodic table, we view that the Lewis electron period diagrams of atoms will never have much more than eight dots about the atomic symbol.

Example 1

What is the Lewis electron dot diagram because that each element?

aluminum selenium


The valence electron construction for aluminum is 3s23p1. So the would have three dots about the symbol for aluminum, 2 of them paired to represent the 3s electrons:

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

For atom with partly filled d or f subshells, these electrons are typically omitted native Lewis electron period diagrams. Because that example, the electron period diagram for iron (valence shell configuration 4s23d6) is together follows:

Elements in the same shaft of the routine table have similar Lewis electron dot diagrams since they have the exact same valence shell electron configuration. Hence the electron period diagrams for the an initial column of facets are together follows:

Monatomic ions space atoms that have actually either lost (for cations) or gained (for anions) electrons. Electron period diagrams because that ions are the same as because that atoms, except that part electrons have been removed for cations, while part electrons have actually been included for anions. For this reason in to compare the electron configurations and electron period diagrams for the Na atom and also the Na+ ion, we keep in mind that the Na atom has actually a solitary valence electron in that Lewis diagram, when the Na+ ion has lost that one valence electron:

Technically, the valence covering of the Na+ ion is now the n = 2 shell, which has eight electron in it. So why carry out we not put eight dots about Na+? Conventionally, as soon as we display electron period diagrams for ions, we present the original valence shell of the atom, which in this case is the n = 3 shell and empty in the Na+ ion.

In making cations, electrons are an initial lost native the highest numbered shell, not 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 electron first, not its 3d electrons, despite the reality that the 3d subshell is the last subshell being filled. Hence we have

Anions have actually extra electron when compared to the initial atom. Below is a to compare of the Cl atom v the Cl− ion:

Example 2

What is the Lewis electron dot diagram because that each ion?

Ca2+ O2−


Having lost its two initial valence electrons, the Lewis electron period diagram is just Ca2+.

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The O2− ion has obtained two electron in the valence shell, for this reason its Lewis electron period diagram is as follows:

Test Yourself

The valence electron construction of thallium, who symbol is Tl, is 6s25d106p1. What is the Lewis electron period diagram because that the Tl+ ion?


Key Takeaways

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

Explain why the first two dots in a Lewis electron period diagram are attracted on the exact same side of the atomic symbol.

Is it crucial for the first dot approximately an atom symbol to go on a details side that the atom symbol?