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Topic: How is magnesium supposedly a chemically weak metal?  (Read 659 times)

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Offline Therapsid

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How is magnesium supposedly a chemically weak metal?
« on: February 24, 2019, 12:44:09 PM »

Wikipedia (https://en.wikipedia.org/wiki/Post-transition_metal#Chemically_weak_metals) says that Rayner-Canham and Overton classify Mg is among the chemically weak metals. Why?

Mg is quite electropositive and ranks high on the reactivity series and the electrochemical series. In fact, in all three respects, it ranks higher than many elements in groups 3 to 12, including elements that are not chemically weak metals. That suggests to me that Mg is a chemically strong metal.

Granted, Mg touches the dividing line between metals and non-metals at a corner, but so does Li because Li lies to the top left of Mg. Because H is a non-metal, the line even borders Li at the top. Does that make Li a chemically weak metal, too?

Also, MgO is completely basic, whereas e.g. chromium has an amphoteric oxide and even an acidic one.

Moreover, Mg can exothermically displace each of the alkali metals Li, Na and K from from their oxides (I also almost couldn't believe it at first, but just take a look at the thermochemical data) and probably Rb and Cs, too. Does that sound like a chemically weak metal?

So, is it at all justified to call Mg chemically weak, and if so, what are the reasons for that?


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