When we drink salt water, we are consuming the sodium and chloride ions, right? We can't consume elemental sodium as it's highly reactive but the consumption of its ions seems to be fine. Does that mean that we can consume ions of all elements?


closed as too broad by Klaus-Dieter Warzecha, Jan, Todd Minehardt, Jannis Andreska, orthocresol Nov 8 '16 at 16:18

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    $\begingroup$ No it does not. I strongly recommend against consuming Hg(2+) ions $\endgroup$ – orthocresol Jun 7 '16 at 17:15
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    $\begingroup$ Everything is toxic in the right dosage. $\endgroup$ – bon Jun 7 '16 at 17:18
  • $\begingroup$ It's just like berries. You should only eat the edible ones. All the others may harm you. $\endgroup$ – aventurin Jun 7 '16 at 18:29


And multiple others...

To clarify a bit further, the hazards from sodium metal and from, say, ionic mercury are different:

Sodium metal is so "eager" to cast away an electron that it will do so quite aggressively when it contacts any aqueous solution, including saliva. It thus represents a "reactivity" or "chemical" hazard in the mouth. Once each $\ce{Na^0}$ has forcibly donated its electron, though, it becomes the non-hazardous $\ce{Na+}$.

Ionic mercury, on the other hand, represents a relatively minor "direct" hazard to the body. Instead, the various forms of mercury interfere with biological/biochemical processes in the body, leading to its severe toxicity. One particular example highlighted in the Wikipedia article on mercury poisoning is the irreversible inhibition of selenoenzymes:

One mechanism of mercury toxicity involves its irreversible inhibition of selenoenzymes, such as thioredoxin reductase .... Although it has many functions, thioredoxin reductase restores vitamins C and E, as well as a number of other important antioxidant molecules, back into their reduced forms, enabling them to counteract oxidative damage. Since the rate of oxygen consumption is particularly high in brain tissues, production of reactive oxygen species is accentuated in these vital cells, making them particularly vulnerable to oxidative damage and especially dependent upon the antioxidant protection provided by selenoenzymes. High mercury exposures deplete the amount of cellular selenium available for the biosynthesis of thioredoxin reductase and other selenoenzymes that prevent and reverse oxidative damage, which, if the depletion is severe and long lasting, results in brain cell dysfunctions that can ultimately cause death.

  • $\begingroup$ Thanks Brian! Your explanation was amazing and really cleared my doubt. However, another question that came to mind after reading your answer was whether or not the position of an element on the periodic table(metals, transition metals and non-metals) has anything to do with the danger its ions poses to humans. For example, as you and @orthocresol have said, sodium ions pose no danger to humans but ionic mercury does. Is this due to sodium being a metal and mercury being a transition metal or is there no way to generalize? $\endgroup$ – Goodyear Jun 8 '16 at 4:14
  • $\begingroup$ @Goodyear Yes, there are general positional trends. This warrants more explanation that just a comment, though -- I recommend asking it as a new question. $\endgroup$ – hBy2Py Jun 8 '16 at 13:28

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