Most atoms do not have actually eight electron in their valence electron shell. Part atoms have actually only a few electrons in their outer shell, while part atoms lack only one or 2 electrons to have an octet. In instances where an atom has actually three or fewer valence electrons, the atom may lose those valence electron quite quickly until what continues to be is a lower shell that has an octet. Atoms that shed electrons get a positive charge together a resultbecause they space left with fewer negatively fee electrons to balance the confident charges the the protons in the nucleus. Positively charged ions are called cations. Most metals become cations as soon as they do ionic compounds.
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A neutral sodium atom is most likely to achieve an octet in its outermost covering by losing its one valence electron.
\<\ceNa \rightarrow Na^+ + e^-\>
The cation created in this way, Na+, is referred to as the sodium ion to differentiate it indigenous the element. The outermost covering of the sodium ion is the second electron shell, which has eight electrons in it. The octet dominance has been satisfied. Figure \(\PageIndex1\) is a graphical explicate of this process.
The names for confident and an adverse ions room pronounced CAT-eye-ons and also ANN-eye-ons, respectively.
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In plenty of cases, aspects that belong to the same group (vertical column) ~ above the periodic table type ions with the very same charge since they have actually the same number of valence electrons. Thus, the routine table becomes a tool for psychic the dues on countless ions. For example, all ions made indigenous alkali metals, the very first column top top the periodic table, have actually a 1+ charge. Ion made native alkaline planet metals, the 2nd group top top the regular table, have actually a 2+ charge. On the various other side that the routine table, the next-to-last column, the halogens, type ions having a 1− charge. Number \(\PageIndex3\) shows just how the charge on numerous ions deserve to be suspect by the place of an element on the regular table. Keep in mind the convention of first writing the number and also then the sign on a ion through multiple charges. The barium cation is composed Ba2+, no Ba+2.