Which Chloride should have the greatest covalent character?

A. NaCl
B. BeCl2
C. KCl
D. BaCl2
E. CaCl2

This is an exam question I had during my last mid-term, and during this exam we only had a periodic table without the electronegativity of the elements.
I picked BaCl2, am I right? And why/why not?

1 Answer
Truong-Son N.
Dec 7, 2017

It would be #"BeCl"_2#. #"BaCl"_2# has nearly the highest ionic character.

The electronegativity, just like ionization energy, increases from the bottom-left to upper-right of the periodic table. Thus, the metal highest on the periodic table (s-block, first two columns) will have an electronegativity closest to that of #"Cl"#.

http://www.sliderbase.com/

To verify with electronegativity values, we should get the lowest difference in electronegativity for the most covalent character.

http://www.dummies.com/education/science/chemistry/

#DeltaEN_("NaCl") = |0.9 - 3.0| = 2.1#

#color(blue)(DeltaEN_("BeCl"_2)) = |1.5 - 3.0| = color(blue)(1.5)#

#DeltaEN_("KCl") = |0.8 - 3.0| = 2.2#

#DeltaEN_("BaCl"_2") = |0.9 - 3.0| = 2.1#

#DeltaEN_("CaCl"_2) = |1.0 - 3.0| = 2.0#

And indeed, it is #"BeCl"_2#, quantitatively.

Now that you see the data, which of these five ionic compounds has the most ionic character? Had your teacher asked you that, you could not do it without data, because one would guess #"BaCl"_2# and not get it quite right.

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