3.2C: Allred-Rochow Electronegativity Values
- Page ID
- 326149
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Allred-Rochow Electronegativity
Allred-Rochow Electronegativity is a measure that determines the values of the electrostatic force exerted by the effective nuclear charge on the valence electrons. The value of the effective nuclear charges is estimated from Slater's rules. The higher charge, the more likely it will attract electrons. Although, Slater's rule are partly empirical. So the Allred-Rochow electronegativity is no more rigid than the Pauling Electronegativity. Allred and Rochow were two chemists who came up with the Allred-Rochow Electronegativity values by taking the electrostatic force exerted by effective nuclear charge, Zeff, on the valence electron. To do so, they came up with an equation:
\[\chi^{AR} = \left(\dfrac{3590 \times Z_{eff}}{r^2_{cov}}\right) + 0.744 \label{1}\]
At the time, the values for the covalent radius, \(r_{cov}\), were inaccurate. Allred and Rochow added certain perimeters so that it would more closely correspond to Pauling's electronegativity scale.
| H 2.20 |
||||||||||||||||
| Li 0.97 |
Be 1.47 |
B 2.01 |
C 2.50 |
N 3.07 |
O 3.50 |
F 4.10 |
||||||||||
| Na 1.01 |
Mg 1.23 |
Al 1.47 |
Si 1.74 |
P 2.06 |
S 2.44 |
Cl 2.83 |
||||||||||
| K 0.91 |
Ca 1.04 |
Sc 1.20 |
Ti 1.32 |
V 1.45 |
Cr 1.56 |
Mn 1.60 |
Fe 1.64 |
Co 1.70 |
Ni 1.75 |
Cu 1.75 |
Zn 1.66 |
Ga 1.82 |
Ge 2.02 |
As 2.20 |
Se 2.48 |
Br 2.74 |
| Rb 0.89 |
Sr 0.99 |
Y 1.11 |
Zr 1.22 |
Nb 1.23 |
Mo 1.30 |
Te 1.36 |
Ru 1.42 |
Rh 1.45 |
Pd 1.35 |
Ag 1.42 |
Cd 1.46 |
In 1.49 |
Sn 1.72 |
Sb 1.82 |
Te 2.01 |
I 2.21 |
| Cs 0.86 |
Ba 0.97 |
La 1.08 |
Hf 1.23 |
Ta 1.33 |
W 1.40 |
Re 1.46 |
Os 1.52 |
Ir 1.55 |
Pt 1.44 |
Au 1.42 |
Hg 1.44 |
Tl 1.44 |
Pb 1.55 |
Bi 1.67 |
Po 1.76 |
At 1.90 |
In this table, the electronegativities increases from left to right just like Pauling's scale because the \(Z\) is increasing. As we go down the group, it decreases because of the larger atomic size that increases the distance between the electrons and nucleus.
References
- Gary Wulfsberg. Inorganic Chemistry. University Science Books, February 2000.
- Housecroft, Catherine E., and Alan G. Sharpe. Inorganic Chemistry. 3rd ed. Harlow: Pearson Education, 2008. Print. (Pg. 43-44)
- Sarah Anderson. Intro to Inorganic Chemistry. University Science Books, September 2004.
- Linus Pauling. General Chemistry. University Science Books, March 2002.
- Leroy G. Wade. Organic Chemistry. 7th ed. Harlow: Pearson Education, 2006.
- John E. McMurry. General Chemistry: Atoms. 1st ed. Harlow: Pearson Education, 2000.
Contributors and Attributions
- Mark Vu