Most atoms execute not have eight electron in your valence electron shell. Part atoms have actually only a few electrons in their outer shell, while some atoms absence only one or 2 electrons to have an octet. In cases where an atom has actually three or under valence electrons, the atom may shed those valence electron quite easily until what stays is a lower shell that consists of an octet. Atom that lose electrons obtain a confident charge together a resultbecause they are left v fewer negatively charged electrons to balance the positive charges the the protons in the nucleus. Positive charged ion are called cations. Many metals become cations when they do ionic compounds.

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Cations

A neutral salt atom is most likely to attain an octet in that outermost shell by shedding its one valence electron.

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

The cation developed in this way, Na+, is called the salt ion to identify it indigenous the element. The outermost shell of the sodium ion is the 2nd electron shell, which has eight electrons in it. The octet preeminence has been satisfied. Figure \(\PageIndex1\) is a graphical depiction of this process.

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

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

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In numerous cases, aspects that belong come the same group (vertical column) on the routine table type ions v the very same charge since they have the same number of valence electrons. Thus, the periodic table becomes a device for mental the charges on plenty of ions. For example, all ions made indigenous alkali metals, the first column ~ above the routine table, have actually a 1+ charge. Ion made native alkaline planet metals, the second group ~ above the regular table, have a 2+ charge. ~ above the various other side the the routine table, the next-to-last column, the halogens, form ions having a 1− charge. Number \(\PageIndex3\) shows just how the charge on countless ions deserve to be guess by the ar of an aspect on the periodic table. Note the convention of first writing the number and also then the sign on a ion with multiple charges. The barium cation is created Ba2+, no Ba+2.