Most atoms do 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 two electrons to have actually an octet. In instances where one atom has actually three or under valence electrons, the atom may lose those valence electron quite easily until what stays is a lower shell that includes an octet. Atom that lose electrons get a confident charge as a resultbecause they space left through fewer negatively fee electrons to balance the positive charges of the protons in the nucleus. Positive charged ions are referred to as cations. Many metals come to be cations when they make ionic compounds.

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A neutral sodium atom is most likely to accomplish an octet in that outermost covering by shedding its one valence electron.

\<\ceNa \rightarrow Na^+ + e^-\>

The cation produced in this way, Na+, is dubbed the salt ion to differentiate it indigenous the element. The outermost covering of the salt ion is the 2nd electron shell, which has eight electrons in it. The octet rule has to be satisfied. Figure \(\PageIndex1\) is a graphical depiction of this process.

api/deki/files/114134/3.2B.jpg?revision=1" />Figure \(\PageIndex2\): The formation of a Chlorine Ion. On the left, the chlorine atom has 17 electrons. ~ above the right, the chloride ion has actually 18 electrons and also has a 1− charge.

The name for hopeful and an adverse ions room pronounced CAT-eye-ons and ANN-eye-ons, respectively.

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In plenty of cases, elements that belong to the same group (vertical column) ~ above the routine table form ions through the same charge since they have the same variety of valence electrons. Thus, the periodic table i do not care a tool for psychic the fees on countless ions. Because that example, all ions made indigenous alkali metals, the an initial column ~ above the periodic table, have a 1+ charge. Ion made indigenous alkaline earth metals, the 2nd group on the regular table, have actually a 2+ charge. ~ above the other side the the regular table, the next-to-last column, the halogens, form ions having a 1− charge. Figure \(\PageIndex3\) shows exactly how the fee on countless ions deserve to be guess by the place of an aspect on the routine table. Keep in mind the convention of very first writing the number and also then the sign on a ion with multiple charges. The barium cation is composed Ba2+, not Ba+2.