Most atoms carry out not have eight electron in their valence electron shell. Part atoms have only a couple of electrons in their outer shell, while part atoms lack only one or two electrons to have an octet. In instances where one atom has three or under valence electrons, the atom may shed those valence electron quite easily until what continues to be is a lower shell that contains an octet. Atoms that lose electrons gain a hopeful charge as a an outcome because they room left with fewer negatively fee electrons come balance the hopeful charges of the protons in the nucleus. Positively charged ions are called cations.

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most metals end up being cations once they make ionic compounds.

Some atom have practically eight electron in your valence shell and can gain extr valence electrons till they have an octet. When these atoms get electrons, they get a an adverse charge because they currently possess more electrons 보다 protons. Negatively fee ions are called anions. many nonmetals come to be anions when they do ionic compounds.


Note

The names for optimistic and an adverse ions are pronounced CAT-eye-ons and also ANN-eye-ons, respectively.


Electron Transfer

We deserve to use electron construction to show the electron transfer process between salt atoms and also chlorine atoms. Remind the electron configuration of salt from thing 2 “Elements, Atoms, and also the routine Table”:

Na: 1s22s22p63s1

As prove in example 1 (in section 3.1 “Two species of Bonding”), salt is most likely to attain an octet in the outermost shell by losing its one valence electron. The remaining varieties has the following electron configuration:



The cation produced in this way, Na+, is called the sodium ion to distinguish it from the element. The outermost shell of the sodium ion is the second electron shell, which has actually eight electrons in it. The octet rule has been satisfied. Figure 3.1 “The formation of a salt Ion” is a graphical explicate of this process.


Figure 3.1 The development of a sodium Ion. On the left, a sodium atom has 11 electrons. On the right, the sodium ion only has 10 electrons and a 1+ charge.


Cl: 1s22s22p63s23p5

Only one more electron is essential to achieve an octet in chlorine’s valence shell. (In table salt, this electron originates from the sodium atom.) The electron configuration of the brand-new species that results is together follows:



In this case, the ion has actually the very same outermost shell as the initial atom, however now that shell has actually eight electron in it. Once again, the octet rule has to be satisfied. The resulting anion, Cl−, is referred to as the chloride ion; note the slight readjust in the suffix (-ide instead of –ine) to develop the surname of this anion. Figure 3.2 “The development of a Chlorine Ion” is a graphical explicate of this process.


Figure 3.2 The formation of a Chlorine Ion. On the left, the chlorine atom has actually 17 electrons. Top top the right, the chloride ion has actually 18 electrons and also has a 1− charge.


With two oppositely charged ions, over there is one electrostatic attraction between them due to the fact that opposite charges attract. The resulting combination is the compound salt chloride. An alert that there room no leftover electrons. The number of electrons shed by the salt atom (one) equates to the variety of electrons got by the chlorine atom (one), so the compound is electrically neutral. In macroscopic samples of sodium chloride, there room billions and also billions the sodium and also chloride ions, although over there is always the same number of cations and anions.


In countless cases, aspects that belong come the same group (vertical column) on the periodic table form ions through the same charge since they have actually the same variety of valence electrons. Thus, the periodic table becomes a tool for remembering the dues on countless ions. For example, all ions made indigenous alkali metals, the an initial column on the periodic table, have actually a 1+ charge. Ions made indigenous alkaline planet metals, the second group top top the routine table, have a 2+ charge. Top top the other side the the regular table, the next-to-last column, the halogens, form ions having actually a 1− charge. Number 3.3 “Predicting Ionic Charges” shows how the fee on plenty of ions can be guess by the place of an aspect on the routine table. Keep in mind the convention of very first writing the number and then the sign on a multiply charged ion. The barium cation is composed Ba2+, no Ba+2.


Figure 3.3 Predicting Ionic Charges. The charge that an atom acquires when it becomes an ion is concerned the framework of the periodic table. In ~ a team (family) of elements, atoms kind ions of a specific charge.


Lewis Diagrams

Chemists use basic diagrams to show an atom’s valence electrons and also how castle transfer. This diagrams have two advantages over the electron shell diagrams introduced in thing 2 “Elements, Atoms, and also the regular Table”. First, they present only valence electrons. Second, instead of having actually a circle approximately the chemistry symbol to represent the electron shell, they have up to eight dots roughly the symbol; each dot represents a valence electron. These dots are arranged to the right and also left and above and below the symbol, v no an ext than 2 dots ~ above a side. Because that example, the depiction for sodium is as follows:




Note

It does not matter what political parties the dots are inserted on in Lewis diagrams as long as each side has actually a maximum of two dots.


These diagrams are dubbed Lewis electron period diagrams, or merely Lewis diagrams, after Gilbert N. Lewis, the American chemist who introduced them. Number 3.4 “Lewis Diagrams that the facets Lithium with Neon” shows the electron configurations and also Lewis diagrams that the facets lithium through neon, i m sorry is the entire second duration of the periodic table. Because that the main team elements, the variety of valence electron is the same as the group number detailed at the top of the periodic table.


Figure 3.4 Lewis Diagrams of the elements Lithium through Neon. 


The transfer of electrons deserve to be depicted easily through Lewis diagrams:



In representing the last formula, the dots are omitted.


Example 2

Starting through lithium and bromine atoms, use Lewis diagrams to present the development of the ionic compound LiBr.


From the regular table, we watch that lithium is in the same pillar as sodium, so the will have the same valence shell electron configuration. That method that the neutral lithium atom will have the very same Lewis diagram that the sodium atom has. Similarly, bromine is in the same obelisk as chlorine, so that will have actually the exact same Lewis diagram that chlorine has. Therefore,

*

Starting through magnesium and also oxygen atoms, usage Lewis diagrams to show the development of the ionic link MgO.

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Some ionic compounds have different numbers of cations and also anions. In those cases, electron carry occurs between an ext than one atom. Because that example, below is the formation of MgBr2:


Most of the aspects that do ionic compounds form an ion that has a properties charge. For example, sodium makes ionic compounds in which the sodium ion always has a 1+ charge. Chlorine renders ionic compound in i m sorry the chloride ion always has a 1− charge. Part elements, especially shift metals, can form ions of lot of charges. Figure 3.5 “Charges that the Monatomic Ions” reflects the characteristic charges for some of these ions. As we experienced in figure 3.1 “The formation of a salt Ion”, there is a sample to the dues on plenty of of the main team ions, but there is no basic pattern for transition metal ions (or for the larger main team elements).