Most atoms perform not have eight electrons in their valence electron shell. Part atoms have only a couple of electrons in their external shell, while part atoms absence only one or 2 electrons to have actually an octet. In instances where an atom has three or fewer valence electrons, the atom may shed those valence electron quite easily until what remains is a reduced shell that includes an octet. Atom that shed electrons acquire a optimistic charge as a an outcome because they room left v fewer negatively charged electrons come balance the confident charges that the proton in the nucleus. Positively charged ion are called cations.

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many metals become cations when they make ionic compounds.

Some atoms have almost eight electrons in their valence shell and can gain added valence electrons until they have an octet. As soon as these atoms get electrons, they obtain a negative charge due to the fact that they currently possess more electrons 보다 protons. Negatively charged ions are called anions. most nonmetals end up being anions as soon as they make ionic compounds.


Note

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


Electron Transfer

We have the right to use electron configurations to illustrate the electron transfer process between salt atoms and chlorine atoms. Remind the electron construction of sodium from thing 2 “Elements, Atoms, and also the regular Table”:

Na: 1s22s22p63s1

As prove in instance 1 (in section 3.1 “Two species of Bonding”), sodium is most likely to attain an octet in the outermost covering by shedding its one valence electron. The remaining types has the complying with electron configuration:



The cation developed in this way, Na+, is called the salt ion to distinguish it from the element. The outermost shell of the sodium ion is the 2nd electron shell, which has actually eight electrons in it. The octet preeminence has been satisfied. Figure 3.1 “The development of a sodium Ion” is a graphical depiction of this process.


Figure 3.1 The formation of a salt Ion. On the left, a salt atom has actually 11 electrons. ~ above the right, the salt ion only has actually 10 electrons and a 1+ charge.


Cl: 1s22s22p63s23p5

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



In this case, the ion has actually the exact same outermost covering as the initial atom, but now the shell has actually eight electron in it. Once again, the octet dominance has been satisfied. The resulting anion, Cl−, is dubbed the chloride ion; keep in mind the slight adjust in the suffix (-ide instead of –ine) to produce 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 17 electrons. Top top the right, the chloride ion has actually 18 electrons and also has a 1− charge.


With 2 oppositely charged ions, there is one electrostatic attraction between them because opposite charges attract. The resulting mix is the compound sodium chloride. Notice that there space no leftover electrons. The variety of electrons shed by the salt atom (one) equals the variety of electrons acquired by the chlorine atom (one), therefore the link is electrically neutral. In macroscopic samples of salt chloride, there room billions and also billions that sodium and chloride ions, although over there is constantly the same number of cations and also anions.


In many cases, elements that belong come the same team (vertical column) on the routine table type ions v the same charge since they have the same number of valence electrons. Thus, the periodic table becomes a tool for remembering the fees on numerous ions. Because that example, all ion made indigenous alkali metals, the first column top top the regular table, have a 1+ charge. Ions made indigenous alkaline earth metals, the second group top top the periodic table, have actually a 2+ charge. On the other side of the routine table, the next-to-last column, the halogens, form ions having a 1− charge. Figure 3.3 “Predicting Ionic Charges” shows how the fee on many ions have the right to be suspect by the place of an aspect on the regular table. Note the convention of an initial writing the number and then the sign on a multiply charged ion. The barium cation is created Ba2+, not Ba+2.


Figure 3.3 Predicting Ionic Charges. The charge that one atom acquires when it i do not care an ion is concerned the structure of the routine table. Within a group (family) of elements, atoms kind ions of a particular charge.


Lewis Diagrams

Chemists use straightforward diagrams to display an atom’s valence electrons and also how lock transfer. This diagrams have actually two advantages over the electron covering diagrams presented in thing 2 “Elements, Atoms, and also the routine Table”. First, they display only valence electrons. Second, rather of having actually a circle about the chemistry symbol to stand for the electron shell, they have up come eight dots approximately the symbol; each period represents a valence electron. These dots space arranged come the right and also left and over and listed below the symbol, v no an ext than two dots top top a side. Because that example, the depiction for salt is together follows:




Note

It go not issue what sides the dots are put on in Lewis diagrams as long as each side has a maximum of 2 dots.


These diagrams are referred to as Lewis electron period diagrams, or simply Lewis diagrams, after Gilbert N. Lewis, the American chemist who introduced them. Figure 3.4 “Lewis Diagrams of the facets Lithium with Neon” reflects the electron configurations and also Lewis diagrams that the elements lithium v neon, which is the whole second period of the periodic table. Because that the main group elements, the number of valence electron is the exact same as the team number provided at the optimal of the regular table.


Figure 3.4 Lewis Diagrams of the elements Lithium through Neon. 


The transfer of electrons can be portrayed easily with Lewis diagrams:



In representing the last formula, the dots room omitted.


Example 2

Starting with lithium and also bromine atoms, use Lewis diagrams to display the development of the ionic compound LiBr.


From the routine table, we watch that lithium is in the same pillar as sodium, so that will have the very same valence shell electron configuration. That way that the neutral lithium atom will have actually the same Lewis diagram the the sodium atom has. Similarly, bromine is in the same pillar 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 compound MgO.

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Some ionic compound have various numbers of cations and also anions. In those cases, electron transfer occurs between much more than one atom. For example, below is the development of MgBr2:


Most that the elements that make ionic compounds type an ion that has a properties charge. For example, sodium makes ionic compounds in i m sorry the salt ion constantly has a 1+ charge. Chlorine renders ionic compounds in which the chloride ion always has a 1− charge. Some elements, especially change metals, can kind ions of multiple charges. Number 3.5 “Charges of the Monatomic Ions” shows the characteristic charges for several of these ions. As we experienced in number 3.1 “The formation of a sodium Ion”, there is a sample to the fees on many of the main team ions, but there is no basic pattern for transition metal ions (or for the bigger main team elements).