Alkaline Earth Metals & Electronegativity

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Alkaline Earth Metals & Electronegativity

Post by BusyBeeh » Sat Apr 29, 2017 10:50 am

As I was watching Lesson 3, Slide#2, I came across the following question:

Metal cations such as calcium and magnesium are often conjugated with drugs to improve bioavailability. These cations are:

a) weakly electronegative
b) alkali metals
c) derived from the atomic loss of two electrons
d) formed by the reduction of their standard states.

...I was able to eliminate b) & d) easily but as far as a), I thought this answer would be a possibility seeming how when we look at the periodic trend of electronegativity, it increases across a period and calcium and magnesium are only in group#2 meaning they should have a low electronegativity. The video says otherwise due to the fact that they are positively charged and need electrons to stabilize that charge. In that case, am I just ignoring the periodic table trend of electronegativity?
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Re: Alkaline Earth Metals & Electronegativity

Post by NS_Tutor_Andrew » Sun Apr 30, 2017 10:24 pm

Hi BusyBeeh,

Great question! A couple things are going on here. First, and most simply, the Q is specifically asking about calcium and magnesium cations, not the elements themselves. The cations are definitely derived from the loss of 2 e-, and that actually makes them pretty stable -- they don't really "want" more electrons after that point.

More generally, your question about electronegativity is insightful. Remember that electronegativity is a spectrum -- although Ca and Mg aren't the least electronegative elements out there, they're definitely on the non-electronegative side. This resource is a handy one to get a quick visual overview of electronegativity values across the periodic table: ... ivity.html. As a ballpark estimate it probably wouldn't make sense to talk about an element being even weakly electronegative until you hit a value of 2 or so. Better to think of the left two or three columns as just not being electronegative in any meaningful sense.

Hope this helps!
Andrew D.
Content Manager, Next Step Test Prep.
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