Most atoms perform not have eight electron in their valence electron shell. Some atoms have actually only a couple of electrons in their outer shell, while part atoms absence only one or two electrons to have an octet. In instances where an atom has three or under valence electrons, the atom may lose those valence electron quite conveniently until what remains is a lower shell that has an octet. Atoms that shed electrons gain a positive charge together a resultbecause they room left through fewer negatively fee electrons come balance the confident charges of the protons in the nucleus. Positive charged ion are dubbed cations. Most metals come to be cations as soon as they make ionic compounds.

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A neutral sodium atom is most likely to achieve an octet in the outermost shell by losing its one valence electron.

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

The cation produced in this way, Na+, is referred to as the salt ion to differentiate it indigenous the element. The outermost covering of the sodium ion is the second electron shell, which has actually eight electron in it. The octet dominion 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. Top top the left, the chlorine atom has 17 electrons. On the right, the chloride ion has 18 electrons and also has a 1− charge.

The names for confident and negative ions room pronounced CAT-eye-ons and ANN-eye-ons, respectively.

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In plenty of cases, elements that belong come the same group (vertical column) on the routine table type ions with the same charge due to the fact that they have actually the same variety of valence electrons. Thus, the periodic table i do not care a tool for mental the fees on numerous ions. For example, all ions made from alkali metals, the an initial column top top the routine table, have a 1+ charge. Ions made indigenous alkaline planet metals, the second group on the regular table, have actually a 2+ charge. ~ above the various other side the the regular table, the next-to-last column, the halogens, form ions having actually a 1− charge. Number \(\PageIndex3\) shows exactly how the fee on plenty of ions deserve to be predicted by the place of an aspect on the periodic table. Note the convention of an initial writing the number and then the authorize on a ion v multiple charges. The barium cation is composed Ba2+, no Ba+2.