# Homework Help: Rank Electronegativity Pairings

1. Nov 18, 2017

### Lori

1. The problem statement, all variables and given/known data

Br2, KBr, and HBr
2. Relevant equations
none

3. The attempt at a solution
I understand that Br2 would be least electronegative because they both equally share the electrons, but i dont 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

2. Nov 18, 2017

### Staff: Mentor

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.

3. Nov 18, 2017

### Lori

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

4. Nov 18, 2017

### Lori

Does anyone know how i can figure out the ranking without knowing the electronegativity values? Perhaps, there is something conceptually i dont know about? I'm confused on how i know the Hbr is less electronegative than Kbr

5. Nov 19, 2017

### I like Serena

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.

6. Nov 30, 2017

### DrDu

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