Curiously, people who suffer from low salt (called hyponatria) do so not because they ingest too little salt but because they drink too much water. The health effects of too much salt are still under debate, although a 2010 report by the US Department of Agriculture concluded that “excessive sodium intake…raises blood pressure, a well-accepted and extraordinarily common risk factor for stroke, coronary heart disease, and kidney disease.” It is clear that most people ingest more salt than their bodies need, and most nutritionists recommend curbing salt intake. The taste of salt is one of the fundamental tastes salt is probably the most ancient flavouring known, and one of the few rocks we eat. Cl − ions are necessary for proper nerve function and respiration. Na + ions are one of the main ions in the human body and are necessary to regulate the fluid balance in the body. (c) Together, sodium and chlorine make sodium chloride-salt-which is necessary for our survival. (b) Chlorine is a pale yellow, noxious gas. The two atoms have these Lewis electron dot diagrams and electron configurations: Now consider an Na atom in the presence of a Cl atom. The octet rule is a result of trends in energies and is useful in explaining why atoms form the ions that they do. It turns out that the Na + ion has a complete octet in its new valence shell, the n = 2 shell, which satisfies the octet rule. However, that requires much more energy than is normally available in chemical reactions, so sodium stops at a 1+ charge after losing a single electron. We could remove another electron by adding even more energy to the ion, to make the Na 2+ ion. It is rather reactive, however, and does not require a lot of energy to remove that electron to make the Na + ion. Consider sodium: in its elemental form, it has one valence electron and is stable. It is not impossible to violate the octet rule. When atoms form compounds, the octet rule is not always satisfied for all atoms at all times, but it is a very good rule of thumb for understanding the kinds of bonding arrangements that atoms can make. The trend that atoms like to have eight electrons in their valence shell is called the octet rule. For whatever reason, having eight electrons in a valence shell is a particularly energetically stable arrangement of electrons. The lower shell, now the valence shell, has eight electrons in it, so the atom becomes positively charged. Either atoms gain enough electrons to have eight electrons in the valence shell and become the appropriately charged anion, or they lose the electrons in their original valence shell. The astute reader may have noticed something: Many of the ions that form have eight electrons in their valence shell. In Section 9.1 “Lewis Electron Dot Diagrams,” we saw how ions are formed by losing electrons to make cations or by gaining electrons to form anions. Demonstrate electron transfer between atoms to form ionic bonds.
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