Alkaline Earth Metals & Electronegativity

User avatar
BusyBeeh
Posts: 42
Joined: Sun Apr 09, 2017 4:47 pm
Location: SoCal
Contact:

Alkaline Earth Metals & Electronegativity

Postby 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?
"Develop success from failures. Discouragement and failure are two of the surest stepping stones to success." ~Dale Carnegie
NS_Tutor_Andrew
Site Admin
Posts: 520
Joined: Mon May 23, 2016 1:47 pm

Re: Alkaline Earth Metals & Electronegativity

Postby 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: https://www.webelements.com/calcium/electronegativity.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.

Return to “Post your questions here about any videos in the class”