specify the two species of ions. Usage Lewis diagrams to illustrate ion formation.

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Most atoms perform not have actually eight electrons in your valence electron shell. Some atoms have only a couple of electrons in their outer shell, while some atoms lack only one or 2 electrons to have actually an octet. In cases where an atom has three or fewer valence electrons, the atom may lose those valence electrons quite conveniently until what remains is a lower shell that consists of an octet. Atom that lose electrons get a optimistic charge together a an outcome because they room left through fewer negatively charged electrons come balance the confident charges that the protons in the nucleus. Positively charged ion are referred to as cations. Many metals become cations once they do ionic compounds.

Some atoms have practically eight electron in their valence shell and also can gain additional valence electrons till they have an octet. When these atoms get electrons, they gain a an unfavorable charge since they currently possess more electrons than protons. Negative charged ion are referred to as anions. Many nonmetals come to be anions when they do ionic compounds.

Electron Transfer

We can use electron configurations to highlight the electron transfer process between salt atoms and also chlorine atoms.

Na: 1s22s22p63s1

As demonstrated here, a salt atom (Na) has one valence electron in the 3rd principal energy level. That is likely to attain an octet in its outermost shell by losing its one valence electron. The cation created in this way, Na+, is referred to as the sodium ion to distinguish it from the element. The sodium ion, Na+, has the electron configuration v an octet of electrons from the 2nd principal power level. That is now the very same as the of the noble gas neon. The term isoelectronic describes an atom and also an ion that a various atom (or two various ions) that have the same electron configuration. The sodium ion is isoelectronic through the neon atom. The equation listed below illustrates this process.

<eginarraylcl ceNa & ightarrow & ceNa^+ + cee^- \ 1s^2 : 2s^2 : 2p^6 : 3s^1 & & 1s^2 : 2s^2 : 2p^6 : ext(octet) endarray>

Figure (PageIndex1) is a graphical depiction of this process.

Figure (PageIndex1): The formation of a salt Ion. Top top the left, a sodium atom has actually 11 electrons. Top top the right, the sodium ion only has 10 electrons and also a 1+ charge.

Now, let"s think about chlorine atom, Cl: 1s22s22p63s23p5

Only one an ext electron is necessary to achieve an octet in chlorine’s valence shell. Once a chlorine atom benefit an electron, that outermost principal energy level achieves an octet. In this case, the ion has actually the very same outermost shell as the original atom, but now the shell has eight electron in it. When again, the octet rule has to be satisfied. The resulting anion, Cl−, is dubbed the chloride ion; note the slight change in the suffix (-ide rather of -ine) to produce the surname of this anion. This procedure is depicted below. (In table salt, this electron comes from the salt atom.)

<eginarraylcl ceCl + cee^- & ightarrow & ceCl^- \ 1s^2 : 2s^2 :2p^6 : 3s^2 : 3p^5 & & 1s^2 : 2s^2 : 2p^6 : 3s^2 : 3p^6 ext(octet) endarray>

Figure (PageIndex2) is a graphical explicate of this process.

Figure (PageIndex2): The development of a Chlorine Ion. ~ above the left, the chlorine atom has 17 electrons. On the right, the chloride ion has 18 electrons and also has a 1− charge.

With two oppositely fee ions, there is one electrostatic attraction between them since opposite dues attract. The resulting mix is the compound salt chloride. An alert that there space no leftover electrons. The number of electrons lost by the salt atom (one) equals the variety of electrons gained by the chlorine atom (one), for this reason the compound is electrically neutral. In macroscopic samples of sodium chloride, there room billions and also billions of sodium and chloride ions, although over there is constantly the same variety of cations and anions.

Example (PageIndex1)

Write the electron configuration of aluminum atom (Z=13). How many electrons should Al lose/gain to achieve octet? compose the formula that the resulting ion and also its electron configuration.


The electron configuration of Al atom is 1s22s22p63s23p1. The second shell has actually octet (2s22p6) when the valence shell has 3 electron (3s23p1). Mg can accomplish octet by losing the 3 valence electrons. The result cation is Al3+ through electron configuration, 1s22s22p6.

Exercise (PageIndex1)

Write the electron configuration of oxygen atom (Z=8). How many electrons must O lose/gain to achieve octet? create the formula of the resulting ion and also its electron configuration.


The electron construction of O atom is 1s22s22p4. The 2nd shell has actually six electrons (2s22p4) and needs two electrons to attain octet. Oxygen will obtain 2 electrons. The result anion is O2 v electron configuration, 1s22s22p6.

In plenty of cases, elements that belong to the same group (vertical column) on the regular table type ions v the same charge since they have the same variety of valence electrons. Thus, the regular table becomes a device for psychic the fees on numerous ions. Because that example, all ion made indigenous alkali metals, the first column ~ above the regular table, have a 1+ charge. Ion made from alkaline planet metals, the 2nd group on the routine table, have a 2+ charge. Top top the other side that the routine table, the next-to-last column, the halogens, type ions having actually a 1− charge. Figure (PageIndex3) shows how the charge on countless ions deserve to be suspect by the place of an element on the regular table. Note the convention of very first writing the number and also then the authorize on a multiply charged ion. The barium cation is created Ba2+, not Ba+2.

Figure (PageIndex3): Predicting Ionic Charges. The charge that an atom acquires once it becomes an ion is concerned the structure of the regular table. In ~ a team (family) of elements, atoms kind ions that a certain charge.

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Figure (PageIndex4) shows the electron configurations and also Lewis diagrams the the elements lithium with neon, i m sorry is the entire second period of the routine table. Because that the main group elements, the number that valence electrons is the same together the group number detailed at the peak of the routine table.

Figure (PageIndex4): Lewis Electron period Diagrams that the elements Lithium v Neon

The transfer of electrons can be illustrated easily through Lewis diagrams: