Many atoms perform not have actually eight electrons in their valence electron shell. Some atoms have actually just a few electrons in their external shell, while some atoms absence just one or 2 electrons to have an octet. In situations wbelow an atom has 3 or fewer valence electrons, the atom might shed those valence electrons fairly conveniently until what continues to be is a lower shell that has an octet. Atoms that shed electrons obtain a positive charge as a resultbereason they are left through fewer negatively charged electrons to balance the positive charges of the protons in the nucleus. Positively charged ions are called cations. Most metals end up being cations when they make ionic compounds.

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Cations

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

The cation produced in this way, Na+, is called the sodium ion to distinguish it from the element. The outera lot of shell of the sodium ion is the second electron shell, which has eight electrons in it. The octet dominion has actually been satisfied. Figure (PageIndex1) is a graphical depiction of this procedure.

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

The names for positive and negative ions are pronounced CAT-eye-ons and also ANN-eye-ons, respectively.

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In many kind of situations, facets that belengthy to the exact same group (vertical column) on the regular table create ions with the very same charge bereason they have the same variety of valence electrons. Therefore, the periodic table becomes a tool for remembering the charges on many kind of ions. For instance, all ions made from alkali metals, the first column on the regular table, have actually a 1+ charge. Ions made from alkaline earth steels, the second group on the regular table, have actually a 2+ charge. On the various other side of the periodic table, the next-to-last column, the halogens, create ions having a 1− charge. Figure (PageIndex3) shows exactly how the charge on many kind of ions can be predicted by the place of an facet on the periodic table. Keep in mind the convention of initially composing the number and also then the sign on a ion through multiple charges. The barium cation is composed Ba2+, not Ba+2.