Rank Electronegativity Pairings

[Lori]

Homework Statement

Br2, KBr, and HBr

Homework Equations

none

The Attempt at a Solution

I understand that Br2 would be least electronegative because they both equally share the electrons, but i don't understand why KBr is more electronegative than HBr. This question was on my quiz, and i wasn't given a table of the electronegatives, so i had to think about it.

Can someone explain how i could find out if one is more electronegative than the other based on the periodic table? Is there like a periodic table trend for electronegativity for bond pairs?

Thanks[/B]

 

[Borek]

Looks to me like you are confused about something. Electronegativity is a property of an element, not of a bond or a substance. Perhaps what you mean is just the difference between electronegativities of the elements involved? If so, it just about subtracting them, no need to look for any explanation.

 

[Lori]

Looks to me like you are confused about something. Electronegativity is a property of an element, not of a bond or a substance. Perhaps what you mean is just the difference between electronegativities of the elements involved? If so, it just about subtracting them, no need to look for any explanation.

I think that's the case. But, it was on my pop quiz for chem and we were told to rank the pairs based on electronegativity. The problem was I didn't* get the electronegative numbers for each element.

Is there a rule to like estimate the differences? I know that Br2 is least electronegative since the difference is 0

 

[Lori]

Does anyone know how i can figure out the ranking without knowing the electronegativity values? Perhaps, there is something conceptually i don't know about? I'm confused on how i know the Hbr is less electronegative than Kbr

 

[I like Serena]

Does anyone know how i can figure out the ranking without knowing the electronegativity values? Perhaps, there is something conceptually i don't know about? I'm confused on how i know the Hbr is less electronegative than Kbr

Hey Lori!

Consider that the periodic system looks like the following with electronegativity.
And note that H and K are both in group 1, and K and Br are both in period 4.

H
$\uparrow$ (increasing electronegativity)
K $\rightarrow$ (increasing electronegativity) Br

From this diagram we can conclude that the difference between Br and K must be greater than the difference between Br and H.

 

[DrDu]

The problem was I didn't* get the electronegative numbers for each element.

Its chemistry, you should have learned them by heart :-)