Re: pinhole Alkaline Earths & Alkalis

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From: Geoff Ruth (gruth@leadershiphigh.org)
Date: Thu Sep 16 2004 - 20:30:14 PDT 

Message-Id: <p0611040fbd7009842aeb@[192.168.123.175]>
Date: Thu, 16 Sep 2004 20:30:14 -0700
From: Geoff Ruth <gruth@leadershiphigh.org>
Subject: Re: pinhole Alkaline Earths & Alkalis

I'll take a stab at this:

Both 1A and 2A metals form basic solutions when dissolved in water.
For example:
Na + H2O --> NaOH + H2
Ca + H2O --> Ca(OH)2 + H2

The further down a group you move, the more reactive they are in
water; Mg won't do anything very quickly when you add it to water,
whereas Ca starts to bubble visibly.

So both 1A and 2A metals are alkaline in solution, like you wrote.
Interestingly, alkaline comes from the Arabic word for ashes
(al-qali) since ashes are basic -- and were used to make soap when
mixed with fats.

As for the earth part, I've read that alchemists noticed that some
minerals (don't know which) containing 2A elements won't react or
melt when they are put in fire. Therefore, alchemists called them
earth elements. (I got this fact from Suchocki's Conceptual Chemistry
book, along with the Arabic al-qali thing.)

Hope this helps,
Geoff

>A student asked me how the alkaline earth metals and alkali metals
>got their names. I know they were named before they could be
>isolated, but why were magnesia, lime and baryta called "alkaline
>earths"? I'm assuming that soda and potash were basic and so they
>were called alkali?
>
>Any clues would be greatly appreciated!
>Rebecah Davis
>
>
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