Electronegativities of the elements (data page)

# Electronegativities of the elements (data page)

Main article: Electronegativity

## Contents

• 1 Electronegativity (Pauling scale)
• 2 Notes
• 3 Electronegativity (Allen scale)
• 4 References
• 4.1 WEL
• 4.2 CRC
• 4.3 LNG
• 4.4 Allen Electronegativities

## Electronegativity (Pauling scale)[ edit ]

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• v
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Periodic table of electronegativity by Pauling scale
→ Atomic radius decreases → Ionization energy increases → Electronegativity increases →
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Group  →
↓  Period
1 H
2.20
He

2 Li
0.98
Be
1.57
B
2.04
C
2.55
N
3.04
O
3.44
F
3.98
Ne

3 Na
0.93
Mg
1.31
Al
1.61
Si
1.90
P
2.19
S
2.58
Cl
3.16
Ar

4 K
0.82
Ca
1.00
Sc
1.36
Ti
1.54
V
1.63
Cr
1.66
Mn
1.55
Fe
1.83
Co
1.88
Ni
1.91
Cu
1.90
Zn
1.65
Ga
1.81
Ge
2.01
As
2.18
Se
2.55
Br
2.96
Kr
3.00
5 Rb
0.82
Sr
0.95
Y
1.22
Zr
1.33
Nb
1.6
Mo
2.16
Tc
1.9
Ru
2.2
Rh
2.28
Pd
2.20
Ag
1.93
Cd
1.69
In
1.78
Sn
1.96
Sb
2.05
Te
2.1
I
2.66
Xe
2.60
6 Cs
0.79
Ba
0.89
La
1.1
Hf
1.3
Ta
1.5
W
2.36
Re
1.9
Os
2.2
Ir
2.20
Pt
2.28
Au
2.54
Hg
2.00
Tl
1.62
Pb
1.87
Bi
2.02
Po
2.0
At
2.2
Rn
2.2
7 Fr
>0.79 [en 1]
Ra
0.9
Ac
1.1
Rf

Db

Sg

Bh

Hs

Mt

Ds

Rg

Cn

Nh

Fl

Mc

Lv

Ts

Og

Ce
1.12
Pr
1.13
Nd
1.14
Pm
1.13
Sm
1.17
Eu
1.2
Gd
1.2
Tb
1.1
Dy
1.22
Ho
1.23
Er
1.24
Tm
1.25
Yb
1.1
Lu
1.27
Th
1.3
Pa
1.5
U
1.38
Np
1.36
Pu
1.28
Am
1.13
Cm
1.28
Bk
1.3
Cf
1.3
Es
1.3
Fm
1.3
Md
1.3
No
1.3
Lr
1.3 [en 2]

Values are given for the elements in their most common and stable oxidation states .

1. ^ The electronegativity of francium was chosen by Pauling as 0.7, close to that of caesium (also assessed 0.7 at that point). The base value of hydrogen was later increased by 0.10 and caesium’s electronegativity was later refined to 0.79; however, no refinements have been made for francium as no experiment has been conducted. However, francium is expected and, to a small extent, observed to be more electronegative than caesium. See francium for details.
2. ^ See Brown, Geoffrey (2012). The Inaccessible Earth: An integrated view to its structure and composition. Springer Science & Business Media. p. 88. ISBN   9789401115162 .

numbersymbolnameuseWELCRCLNG
1H hydrogen2.20same
2He heliumno datasame
3Li lithium0.98same
4Be beryllium1.57same
5B boron2.04same
6C carbon2.55same
7N nitrogen3.04same
8O oxygen3.44same
9F fluorine3.983.983.983.90
10Ne neonno datasame
11Na sodium0.93same
12Mg magnesium1.31same
13Al aluminium1.61same
14Si silicon1.90same
15P phosphorus2.19same
16S sulfur2.58same
17Cl chlorine3.16same
18Ar argonno datasame
19K potassium0.82same
20Ca calcium1.00same
21Sc scandium1.36same
22Ti titanium1.54same
24Cr chromium1.66same
25Mn manganese1.55same
26Fe iron1.83same
27Co cobalt1.88same
28Ni nickel1.91same
29Cu copper1.90same
30Zn zinc1.65same
31Ga gallium1.81same
32Ge germanium2.01same
33As arsenic2.18same
34Se selenium2.55same
35Br bromine2.96same
36Kr krypton3.003.00no datano data
37Rb rubidium0.82same
38Sr strontium0.95same
39Y yttrium1.22same
40Zr zirconium1.33same
41Nb niobium1.6same
42Mo molybdenum2.16same
43Tc technetium1.91.92.102.10
44Ru ruthenium2.2same
45Rh rhodium2.28same
47Ag silver1.93same
49In indium1.78same
50Sn tin1.96same
51Sb antimony2.05same
52Te tellurium2.1same
53I iodine2.66same
54Xe xenon2.62.62.60no data
55Cs caesium0.79same
56Ba barium0.89same
57La lanthanum1.10same
58Ce cerium1.12same
59Pr praseodymium1.13same
60Nd neodymium1.14same
61Pm promethiumno datasame
62Sm samarium1.17same
63Eu europiumno datasame
65Tb terbiumno datasame
66Dy dysprosium1.22same
67Ho holmium1.23same
68Er erbium1.24same
69Tm thulium1.25same
70Yb ytterbiumno datasame
71Lu lutetium1.271.271.01.0
72Hf hafnium1.3same
73Ta tantalum1.5same
74W tungsten2.362.361.71.7
75Re rhenium1.9same
76Os osmium2.2same
77Ir iridium2.202.202.22.2
78Pt platinum2.282.282.22.2
79Au gold2.542.542.42.4
80Hg mercury2.002.001.91.9
81Tl thallium1.621.621.81.8
83Bi bismuth2.022.021.91.9
84Po polonium2.0same
85At astatine2.2same
87Fr franciumno data0.7
89Ac actinium1.1same
90Th thorium1.3same
91Pa protactinium1.5same
92U uranium1.381.381.71.7
93Np neptunium1.361.361.31.3
94Pu plutonium1.281.281.31.3
95Am americium1.31.3no data1.3
96Cm curium1.31.3no data1.3
97Bk berkelium1.31.3no data1.3
98Cf californium1.31.3no data1.3
99Es einsteinium1.31.3no data1.3
100Fm fermium1.31.3no data1.3
101Md mendelevium1.31.3no data1.3
102No nobelium1.31.3no data1.3

## Notes[ edit ]

• Separate values for each source are only given where one or more sources differ.
• Electronegativity is not a uniquely defined property and may depend on the definition. The suggested values are all taken from WebElements as a consistent set.
• Many of the highly radioactive elements have values that must be predictions or extrapolations, but are unfortunately not marked as such. This is especially problematic for francium, which by relativistic calculations can be shown to be less electronegative than caesium, but for which the only value (0.7) in the literature predates these calculations.

## Electronegativity (Allen scale)[ edit ]

• v
• t
• e
Electronegativity using the Allen scale
Group  → 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
↓  Period
1 H
2.300
He
4.160
2 Li
0.912
Be
1.576
B
2.051
C
2.544
N
3.066
O
3.610
F
4.193
Ne
4.787
3 Na
0.869
Mg
1.293
Al
1.613
Si
1.916
P
2.253
S
2.589
Cl
2.869
Ar
3.242
4 K
0.734
Ca
1.034
Sc
1.19
Ti
1.38
V
1.53
Cr
1.65
Mn
1.75
Fe
1.80
Co
1.84
Ni
1.88
Cu
1.85
Zn
1.59
Ga
1.756
Ge
1.994
As
2.211
Se
2.424
Br
2.685
Kr
2.966
5 Rb
0.706
Sr
0.963
Y
1.12
Zr
1.32
Nb
1.41
Mo
1.47
Tc
1.51
Ru
1.54
Rh
1.56
Pd
1.58
Ag
1.87
Cd
1.52
In
1.656
Sn
1.824
Sb
1.984
Te
2.158
I
2.359
Xe
2.582
6 Cs
0.659
Ba
0.881
Lu
1.09
Hf
1.16
Ta
1.34
W
1.47
Re
1.60
Os
1.65
Ir
1.68
Pt
1.72
Au
1.92
Hg
1.76
Tl
1.789
Pb
1.854
Bi
2.01
Po
2.19
At
2.39
Rn
2.60
7 Fr
0.67
Ra
0.89
NumberSymbolNameElectronegativity
1H hydrogen 2.300
2He helium 4.160
3Li lithium 0.912
4Be beryllium 1.576
5B boron 2.051
6C carbon 2.544
7N nitrogen 3.066
8O oxygen 3.610
9F fluorine 4.193
10Ne neon 4.787
11Na sodium 0.869
12Mg magnesium 1.293
13Al aluminium 1.613
14Si silicon 1.916
15P phosphorus 2.253
16S sulfur 2.589
17Cl chlorine 2.869
18Ar argon 3.242
19K potassium 0.734
20Ca calcium 1.034
21Sc scandium 1.19
22Ti titanium 1.38
24Cr chromium 1.65
25Mn manganese 1.75
26Fe iron 1.80
27Co cobalt 1.84
28Ni nickel 1.88
29Cu copper 1.85
30Zn zinc 1.59
31Ga gallium 1.756
32Ge germanium 1.994
33As arsenic 2.211
34Se selenium 2.424
35Br bromine 2.685
36Kr krypton 2.966
37Rb rubidium 0.706
38Sr strontium 0.963
39Y yttrium 1.12
40Zr zirconium 1.32
41Nb niobium 1.41
42Mo molybdenum 1.47
43Tc technetium 1.51
44Ru ruthenium 1.54
45Rh rhodium 1.56
47Ag silver 1.87
49In indium 1.656
50Sn tin 1.824
51Sb antimony 1.984
52Te tellurium 2.158
53I iodine 2.359
54Xe xenon 2.582
55Cs caesium 0.659
56Ba barium 0.881
71Lu lutetium 1.09
72Hf hafnium 1.16
73Ta tantalum 1.34
74W tungsten 1.47
75Re rhenium 1.60
76Os osmium 1.65
77Ir iridium 1.68
78Pt platinum 1.72
79Au gold 1.92
80Hg mercury 1.76
81Tl thallium 1.789
83Bi bismuth 2.01
84Po polonium 2.19
85At astatine 2.39
87Fr francium 0.67

## References[ edit ]

### WEL[ edit ]

As quoted at http://www.webelements.com/ from these sources:

• A.L. Allred, J. Inorg. Nucl. Chem., 1961, 17, 215.
• J.E. Huheey, E.A. Keiter, and R.L. Keiter in Inorganic Chemistry : Principles of Structure and Reactivity, 4th edition, HarperCollins, New York, USA, 1993.

### CRC[ edit ]

As quoted from these sources in an online version of: David R. Lide (ed), CRC Handbook of Chemistry and Physics, 84th Edition. CRC Press. Boca Raton, Florida, 2003; Section 9, Molecular Structure and Spectroscopy; Electronegativity

• Pauling, L., The Nature of the Chemical Bond, Third Edition, Cornell University Press, Ithaca, New York, 1960.
• Allen, L.C., J. Am. Chem. Soc., 111, 9003, 1989.

### LNG[ edit ]

As quoted from these sources in: J.A. Dean (ed), Lange’s Handbook of Chemistry (15th Edition), McGraw-Hill, 1999; Section 4; Table 4.5, Electronegativities of the Elements.

• L. Pauling, The Chemical Bond, Cornell University Press, Ithaca, New York, 1967.
• L. C. Allen, J. Am. Chem. Soc. 111:9003 (1989).
• A. L. Allred J. Inorg. Nucl. Chem. 17:215 (1961).

### Allen Electronegativities[ edit ]

Three references are required to cover the values quoted in the table.

• L. C. Allen, J. Am. Chem. Soc. 111:9003 (1989).
• J. B. Mann, T. L. Meek and L. C. Allen, J. Am. Chem. Soc. 122:2780 (2000).
• J. B. Mann, T. L. Meek, E. T. Knight, J. F. Capitani and L. C. Allen, J. Am. Chem. Soc. 122:5132 (2000).
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# Electronegativity

After
atomic number, mass & valency, electronegativity is the most important
of all atomic parameters.

This page is expanded into a full paper, Electronegativity as a Basic Elemental Property, by Mark Leach available here (PDF).

## The History of Electronegativity

In 1895 the Danish thermochemist Hans Peter J�rgen Julius Thomsen proposed a periodic table that shows electropositive and electronegative elements:

The concept of electronegativity
was put on a quantitative footing in 1932 by Linus
Pauling in The Nature
of the Chemical Bond. IV. The Energy of Single Bonds and the Relative
Electronegativity of Atoms
, Journal of the American
Chemical Society, 54, p. 3570-3582. The original paper is available in HTML here .

In his textbook The Nature of The Chemical Bond (published 1938, quote from 3rd ed.), Pauling says about the atomic property of electronegativity:

"The power of
an atom in a molecule to attract electrons to itself
."

In his General Chemistry textbook (pp 183) Pauling writes:

"It has been found possible to assign to the elements numbers representing their power of attraction for the electrons in a covalent bond, by means of which the amount of partial ionic character may be estimated."

The IUPAC Gold Book says :

"Concept introduced by L. Pauling as the power of an atom to attract electrons to itself. There are several definitions. According to Mulliken it is the average of the ionization energy and electron affinity of an atom, but more frequently a relative scale due to Pauling is used where dimensionless relative electronegativity differences are defined on the basis of bond dissociation energies", here .

As discussed here , this author’s definition is:

"Electronegativity is measure, integrated over numerous physical
parameters, of the power of a gas phase or bonded atom to attract electrons to itself.
"

While
not too much should be read into absolute values, many trends in structure
and reactivity behavior can be mapped to ("explained in terms of",
or correlated with) Pauling’s electronegativity data.
This
makes electronegativity an extraordinarily useful concept.

• There is a broad sweep of electronegativity from top-right to bottom-left. (The radioactive elements francium, Fr, & radium Ra, are ignored as are the lighter group 18 elements: helium, He, neon, Ne, and argon, Ar.)

• The electronegative elements, found top-right, present as non-metals. Fluorine, F2, oxygen, O2, & chlorine, Cl2, are strong oxidising agents: they accept electrons and are easily reduced. The electronegative elements all form anions and they may form entities that interact via lone-pairs of electrons. Anions and electron lone pairs are associated with Lewis base behaviour.

• The electropositive elements all present as metals. Metals behave as electron donating reducing agents. Metals form cations that behave as Lewis acids.

• Hydrogen
is shown above and between boron
and carbon.
This is because the CH bond is polarised δ-CHδ+ and the BH bond is polarised δ+BHδ.
IUPAC are considering the position of hydrogen on their official periodic
table, here .

 In this web book, electronegative elements are coloured blue and electropositive elements are coloured red. The rational is that: Electronegative elements tend to gain electrons to become anionic Lewis bases.Chlorine, eneg 3.16, generally reacts to become chloride ion, Cl, a lobe-HOMO Lewis base. During this process, the chlorine is reduced, so chlorine is an oxidising agent.Electropositive elements, metals, generally react by losing one or more electrons to become cationic Lewis acids.Lithium, eneg 0.98, generally reacts to become Li+, an s-LUMO Lewis acid. Lithium loses an electron so it is oxidised, and so it is acting as a reducing agent.Using this colour representation, the top-right to bottom-left diagonal trend can be clearly seen across the main group elements and across the entire periodic table:

## Why Is Electronegativity Important?

The metallic elements are all electropositive, the electronegative elements are all non-metals, the metalloids are found at intermediate electronegativities.

Ionic compounds, like sodium chloride NaCl, or Na+ Cl, are formed between between electropositive elements (Na, 0.93) and electronegative elements (Cl, 3.16).

Thus it follows that bond type, material character and chemical reactivity can be predicted from a knowledge of electronegativity.

For example:

• Hydrogen chloride, HCl. Chlorine, 3.16, is more electronegative than hydrogen, 2.20, so the H–Cl bond will be polarised Hδ+–Clδ–. This is pronounced "delta plus" and "delta minus". This tells us that HCl will react as H+ and Cl, and HCl is a proton donating Brønsted acid.
• Methyl bromide, CH3Br, has a C–Br bond that is polarised Cδ+–Brδ– and the carbon atom in the molecule is susceptible to nucleophilic substitution.
• There are many examples like this in chemistry.

## Where Do The Numbers Come From?

Pauling’s empirical electronegativity
scale is derived from thermochemical bond-energy data. Pauling observed
that bond enthalpy, EA-B, in kcal/mol between
atoms A and B can be predicted using the equation, where
ΧA and ΧB:
are the electronegativity values of A and B.

In his book The
Nature of The Chemical Bond
, Pauling comments that it is more accurate
to use the geometric mean rather than the arithmetic mean, but then
uses the arithmetic mean himself. Other authors note this and then also
use the arithmetic mean.

Calculations for the formation
of the halogen halides: HF, HCl, HBr & HI from hydrogen, H2,
and the halogens, F2, Cl2,
Br2
&
I2 show how the Pauling relationship compares with
experimental data:

spreadsheet here . Data is from Pauling’s Nature
of the Chemical Bond. Note that the equation requires data to be in
kcal/mol rather than kJ/mol.

The electronegativity
difference between elements A and B is determined from the
following relationships:

Note that both the
geometric and arithmetic mean relationships are given.
For many metals the enthalpy of salt formation data is used as a proxy.

Once a set of electronegativity
differences are known, it is a simple matter to assign absolute electronegativity
values.

## Compounds & Materials, Structure & Reactivity

Chlorine, by way of example,
is the third most electronegative element after fluorine and oxygen. This
electronegative nature is apparent in the structure and reaction chemistry
of:

• The chlorine atom, Cl
• The dichlorine molecule,
Cl2
• Ionic sodium chloride,
NaCl
• Molecular chloromethane,
CH3Cl
• etc.
• Electronegativity can be
used to predict the dipole moment (bond polarity) of a bond:

• Electronegativity can be
used to approximately predict the degree of ionic (and therefore covalent)
character of a bond between two dissimilar elements:

Captured from The
Nature of The Chemical Bond
, 3rd Ed, pp99. The experimental values
are from vapour phase dipole moments.

• Electronegativity can be
used to predict metallic, ionic, covalent and intermediate bond type,
and these behaviours can be mapped to the Van Arkel-Ketelaar Triangle
of Bonding
, as discussed in detail on the next page of the Chemogenesis
web book, here .

• When valency is included
as an additional parameter, electronegativity can be mapped to the Laing
Tetrahedron of Bonding & Material Type
, as discussed on the
next but one page of the Chemogenesis web book, here .

• Electronegativity can be
used to predict chemical reactivity because: “The most stable arrangement
of [polar] covalent bonds connecting a group of atoms is that arrangement
in which the atom with the highest electronegativity be bonded to the
atom with the lowest electronegativity.
” Jolly, Modern Inorganic Chemistry,
McGraw-Hill (1985) pp 61-62.

It follows that pairs of compounds of the type A-Bm
and X-Yn will react with each other to maximise
and minimise electronegativity difference, as discussed on this page of The Chemogenesis web book: Why
Do Chemical Reactions Happen?
, here .

• Electronegativity, along
with bond-length, pKa and other data, is
central to the chemogenesis analysis, as discussed in the sections of
this web book: Quantifying Congeneric Behaviour and Congeneric
Array Interactions
, here
and here .

## Electronegativity and Theory

Pauling used bond enthalpy
data to construct his electronegativity scale. Other workers have used
other starting points.

 Eneg Scale Method Pauling Scale 1932 Obtains values by thermochemical methods. Paper Mulliken Relation 1934 Defines a relation that depends upon the orbital characteristics of an atom in a molecule. Mulliken electronegativity is the numerical average of the ionisation potential and electron affinity. Wikipedia Gordy Scale 1946 Defines electronegativity in terms of the effective nuclear charge and the covalent radius. (Zeff)e/r. Phys. Rev. 69, 604 – 607 (1946) Gordy developed several scales! Walsh Scale 1951 Relates electronegativity to stretching force constants of the bonds of an atom to a hydrogen atom. Abstract Huggins Scale 1953 Alternative to Pauling’s thermochemical procedure. Paper Sanderson Scale 1955 The ratio of the average electron density of an atom to that of a hypothetical "inert" atom having the same number of electrons. This ratio is a measure of the relative compactness of the atom. J.Chem.Phys. 23, 2467 (1955) Allred-Rochow Scale 1958 Defines electronegativity in terms of the effective nuclear charge and covalent radius. Like the Gordy scale but uses (Zeff)e/r2. Wikipedia Jaffe Scale 1962 Uses the electronegativity of orbitals rather than atoms to develop group electronegativities for molecular fragments (eg. CH3 vs CF3) that take into account the charge of a group, the effects of substituents, and the hybridization of the bonding orbital. Electronegativity. I. Orbital Electronegativity of Neutral Atoms J. Hinze and H.H.Jaffe, J.Am.Chem. Soc., 1962, 84, 540 Phillips Scale 1968 Defines electronegativity in terms of the dielectric properties of atoms in a given valence state. Paper Martynov & Batsanov Scale 1980 Obtained by averaging the successive ionisation energies of an element’s valence electrons. Russ. J. Inorg. Chem., 1980, 25, 1737 . Allen CE Scale 1992 Configuration energy (CE), the average one-electron valence shell energy of the ground-state free atom, is used to quantify metal-covalent-ionic bonding, J.Am.Chem.Soc ., (1992), 114, 1510 Lang & Smith2015 Peter F. Lang & Barry C. Smith presented a paper: An equation to calculate internuclear distances of covalent, ionic and metallic lattices, Phys. Chem. Chem. Phys., 2015, 17, 3355 . Quoted from the paper:"At the beginning of our work we used different sets of electronegativities, for example the set developed by Allred & Rochow to calculate internuclear distances of inorganic lattices but find that none of them suit the needs of this work. We first considered that electronegativity values are functions of electron affinities and ionisation energies. We produced many sets of electronegativity values based on generally accepted values of electron affinities and ionisation energies but none of them were satisfactory. Finally, we produced a set deduced from the ionisation energies adjusted for pairing and exchange interactions. This set of electronegativity scales as shown in Table 13 improved the agreement between the calculated and the observed internuclear distances. There are some elements such as technetium and polonium, where little observed data on bond lengths or radii or lattice energies are available. In such cases, their electronegativities are estimated by interpolation/extrapolation of electronegativities of neighbouring elements."

More in: H.B. Michaelson,
IBM
J. Res. Develop. 22 1 (1978) . Review article by H. O. Pritchard
and H. A. Skinner: The
Concept Of Electronegativity, Chem. Rev.; 1955; 55(4) pp 745 – 786 .

Electronegativity seems to
integrate  average  a number of arcane atomic electronic parameters.
It is a proxy parameter that in a rather simple way maps to chemical structure
and reactivity.

In his 1992 paper (J.Am.Chem.Soc., (1992), 114, 1510), Allen argued that configuration energy, CE, is a fundamental atomic property and is the “missing third dimension to the periodic table”. He further stated that electronegativity is an ‘ad hoc‘ parameter.

More usefully 
in this author’s judgment Allen’s work shows that configuration
energy, CE, correlates with electronegativity.

Indeed, electronegativity
is so important that in this author’s judgment it should be considered
to be a basic atomic property rather than a simple atomic property, here .

In 1960 Pauling defined electronegativity as:

"The power of an atom in a molecule to attract
electrons to itself"

However, when considered in the context of semiquantitative
tetrahedra of structure of bonding and material type, this statement is literally too
narrow because bulk binary compounds can be metallic, ionic or network covalent as well as
molecular.

Any definition of electronegativity must not be self-limiting.
An updated definition is:

"Electronegativity is measure, integrated over numerous physical
parameters, of the power of a gas phase or bonded atom to attract electrons to itself
."

## Tables of Electronegativity Data

 Electronegativity Pauling Revised Pauling Mulliken Sanderson Allred- Rochow Lang & Smith 1 H Hydrogen 2.1 2.20 2.8 2.31 2.20 2.00 2 He Helium 3 Li Lithium 1.0 0.98 1.3 0.86 0.97 1.24 4 Be Beryllium 1.5 1.57 1.61 1.47 2.14 5 B Boron 2.0 2.04 1.8 1.88 2.01 1.81 6 C Carbon 2.5 2.55 2.5 2.47 2.50 2.30 7 N Nitrogen 3.0 3.04 2.9 2.93 3.07 2.82 8 O Oxygen 3.5 3.44 3.0 3.46 3.50 3.39 9 F Fluorine 4.0 3.98 4.1 3.92 4.10 4.00 10 Ne Neon 11 Na Sodium 0.9 0.93 1.2 0.85 1.01 1.18 12 Mg Magnesium 1.2 1.31 1.42 1.23 1.76 13 Al Aluminum 1.5 1.61 1.4 1.54 1.47 1.31 14 Si Silicon 1.8 1.90 2.0 1.74 1.74 1.66 15 P Phosphorus 2.1 2.19 2.3 2.16 2.06 2.05 16 S Sulfur 2.5 2.58 2.5 2.66 2.44 2.49 17 Cl Chlorine 3.0 3.16 3.3 3.28 2.83 2.95 18 Ar Argon 3.92 19 K Potassium 0.8 0.82 1.1 0.74 0.91 1.00 20 Ca Calcium 1.0 1.00 1.06 1.04 1.40 21 Sc Scandium 1.3 1.36 1.09 1.20 1.51 22 Ti Titanium 1.5 1.54 1.57 23 V Vanadium 1.6 1.63 1.62 24 Cr Chromium 1.6 1.66 1.65 25 Mn Manganese 1.5 1.55 1.71 26 Fe Iron 1.8 1.83 1.77 27 Co Cobalt 1.8 1.88 1.84 28 Ni Nickel 1.8 1.91 1.92 29 Cu Copper 1.9 1.90 2.02 30 Zn Zinc 1.6 1.65 1.86 1.66 2.16 31 Ga Gallium 1.6 1.81 1.4 2.10 1.82 1.31 32 Ge Germanium 1.8 2.01 1.9 2.31 2.02 1.62 33 As Arsenic 2.0 2.18 2.2 2.53 2.20 1.95 34 Se Selenium 2.4 2.55 2.4 2.76 2.48 2.30 35 Br Bromine 2.8 2.96 3.0 2.96 2.74 2.67 36 Kr Krypton 2.90 3.17 37 Rb Rubidium 0.8 0.82 1.0 0.70 0.89 0.96 38 Sr Strontium 1.0 0.95 0.96 0.99 1.31 39 Y Yttrium 1.2 1.22 1.4 0.98 1.11 1.54 40 Zr Zirconium 1.4 1.33 1.57 41 Nb Niobium 1.6 1.60 1.61 42 Mo Molybdenum 1.8 2.16 1.66 43 Tc Technetium 1.9 1.90 1.71 44 Ru Ruthenium 2.2 2.20 1.76 45 Rh Rhodium 2.2 2.28 1.84 46 Pd Palladium 2.2 2.20 1.91 47 Ag Silver 1.9 1.93 1.92 48 Cd Cadmium 1.7 1.69 1.73 1.46 2.06 49 In Indium 1.7 1.78 1.3 1.88 1.49 1.26 50 Sn Tin 1.8 1.96 1.8 2.02 1.72 1.49 51 Sb Antimony 1.9 2.05 2.0 2.19 1.82 1.73 52 Te Tellurium 2.1 2.10 2.2 2.34 2.01 2.01 53 I Iodine 2.5 2.66 2.7 2.50 2.21 2.32 54 Xe Xenon 2.63 55 Cs Cesium 0.7 0.79 1.0 0.69 0.86 0.89 56 Ba Barium 0.9 0.89 0.93 0.97 1.20 57 La Lanthanum 1.1 1.10 0.92 1.08 1.28 58 Ce Cerium 1.1 1.12 1.27 59 Pr Praseodymium 1.1 1.13 1.25 60 Nd Neodymium 1.1 1.14 1.27 61 Pm Promethium 1.1 1.13 1.28 62 Sm Samarium 1.1 1.17 1.30 63 Eu Europium 1.1 1.20 1.30 64 Gd Gadolinium 1.1 1.20 1.41 65 Tb Terbium 1.1 1.20 1.35 66 Dy Dysprosium 1.1 1.22 1.36 67 Ho Holmium 1.1 1.23 1.38 68 Er Erbium 1.1 1.24 1.40 69 Tm Thulium 1.1 1.25 1.42 70 Yb Ytterbium 1.1 1.10 1.44 71 Lu Lutetium 1.1 1.27 1.25 72 Hf Hafnium 1.3 1.30 1.57 73 Ta Tantalum 1.5 1.50 1.73 74 W Tungsten 1.7 2.36 1.81 75 Re Rhenium 1.9 1.90 1.80 76 Os Osmium 2.2 2.20 1.94 77 Ir Iridium 2.2 2.20 2.06 78 Pt Platinum 2.2 2.28 2.06 79 Au Gold 2.4 2.54 2.12 80 Hg Mercury 1.9 2.00 1.92 1.44 2.40 81 Tl Thallium 1.8 2.04 1.96 1.44 1.34 82 Pb Lead 1.8 2.33 2.01 1.55 1.51 83 Bi Bismuth 1.9 2.02 2.06 1.67 1.68 84 Po Polonium 2.0 2.00 1.90 85 At Astatine 2.2 2.20 2.12 86 Rn Radon 87 Fr Francium 0.7 0.70 88 Ra Radium 0.9 0.90 89 Ac Actinium 1.1 1.10 90 Th Thorium 1.3 1.30 91 Pa Protactinium 1.5 1.50 92 U Uranium 1.7 1.38 93 Np Neptunium 1.3 1.36 94 Pu Plutonium 1.3 1.28

A plot of the above data shows that, broadly, the various electronegativity systems are numerically equivalent:

This page is expanded into a full paper, Electronegativity as a Basic Elemental Property, by Mark Leach available here .

• Linus
Pauling
• Electronegativity
& Pauling Scale
• Mulliken
scale
• Allred-Rochow
scale

& bond character calculator spreadsheet, here .

Thanks to Bruce

 Binary Compound Synthlet Binary Materials: van Arkel-Ketelaar Triangles

Queries, Suggestions, Bugs, Errors, Typos…

If you have any:

Queries
Suggestions

contact Mark R. Leach, the author, using [email protected]

This free, open
access
web book is an ongoing project and your input is appreciated.

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# Electronegativity of zinc vs copper in galvanic cell

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I am reading up on how galvanic cell works and I realised that the flow of electrons is from Zn to Cu. But Zn is more electronegative compared to Cu according to periodic table trends

I read it somewhere that when comparing transition metals, it may be different, but it was not further elaborated. Can someone explain this to me how Cu is more electronegative than Zn?

physical-chemistry electrochemistry

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edited Nov 21 ’12 at 23:17

jonsca

1,76062451

asked Nov 21 ’12 at 6:15

edelweiss

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There are two common confusions in your question. I hope I can clear them up.

Electrons are not flowing from zinc to copper. Not exactly.

In the Zinc-Copper galvanic cell, the net reaction is:

$$\ceZn(s) + Cu^2+ (aq) \ce-> Zn^2+ (aq)\ce + Cu(s)$$

Zinc is being oxidized:

$$\ceZn(s)->Zn^2+(aq) \ce+2e-$$

Copper is being reduced:

$$\ceCu^2+(aq)\ce+2e- ->Cu(s)$$

Electrons, therefore are being transferred from zinc not to copper, but copper (II) ions, which are different than the copper atoms in Cu(s). We need to be comparing something about zinc atoms and copper (II) ions.

Electronegativity has nothing to do with electrochemistry.

Electronegativity is the attraction an atom has for a pair of electrons in a covalent bond.

Electrochemistry is about controlling the electron transfer that accompanies a redox reaction. Usually this involves ionic species, and so electronegativity is not the relevant quantity to compare. In this case, we care about the energy change that occurs when copper and zinc lose electrons (ionization energy) and the stability of the resulting ions in solution. Ionization data mined from this NIST publication .

For zinc:
$$\ceZn->Zn+ + e- \ \ \ \ \ \Delta H= 9.585\times 10^2 \text kJ/mol$$
$$\ceZn+->Zn^2+\ce + e- \ \ \ \ \ \Delta H= 1.733\times 10^3 \text kJ/mol$$
$$\ceZn->Zn^2+ \ce+ 2e- \ \ \ \ \ \Delta H= 2.692\times 10^3 \text kJ/mol$$

For copper:
$$\ceCu->Cu+ + e- \ \ \ \ \ \Delta H= 7.454\times 10^2 \text kJ/mol$$
$$\ceCu+->Cu^2+\ce + e- \ \ \ \ \ \Delta H= 1.958\times 10^3 \text kJ/mol$$
$$\ceCu->Cu^2+ \ce+ 2e- \ \ \ \ \ \Delta H= 2.703\times 10^3 \text kJ/mol$$

Why is zinc oxidized and copper reduced?

Because doing so leads to a lower energy state. It takes more energy to remove two electrons from copper than to remove two electrons from zinc. Thus, to get a negative energy change (spontaneous), when need to add the zinc reaction as written and the copper reaction in reverse:

$$\ceZn->Zn^2+ \ce+ 2e- \ \ \ \ \ \Delta H= 2.692\times 10^3 \text kJ/mol$$
$$\ceCu^2+ \ce+ 2e- -> Cu(s) \ \ \ \ \ \Delta H= -2.703\times 10^3 \text kJ/mol$$
$$\ceZn(s) + Cu^2+ (aq) \ce-> Zn^2+ (aq)\ce + Cu(s)\ \ \ \Delta H= -11 \text kJ/mol$$

The estimate above assumes that the solvation energies of both ions are similar and their standard entropies are similar. I could not find a good source of those data.

In electrochemistry, we care more about the potential of the cell, $E_cell$, which is the potential for the cell to do electrical work. Potential, $E$, is related to free energy change $\Delta G$ by the following equation, where $n$ is the number of moles of electrons transferred and $F$ is Faraday’s constant $F=96,485 \frac\textJ\textV mol$.

$$\Delta G=-nFE$$

For a process to be spontaneous, $\Delta G$ must be negative. $\Delta G$ is negative when $E$ is positive. Thus, in a galvanic cell, electrons will flow in the direction that produces a positive cell potential.

How can we determine which direction that is? First, we could set up the zinc-copper cell, and connect it into a circuit and let it run. In this cell, a piece of copper metal serves as one electrode and a piece of zinc metal serves as the other. Whichever electrode increased in mass is the electrode at which reduction occurred: metals cations are converted to metal atoms, coming out of solution and increasing the mass of the electrode. The other electrode must be the one responsible for oxidation (metal atoms become cations and dissolve away); the mass of this electrode must decrease.

Or, we could do a simpler experiment. Dip a piece of copper metal into a solution of Zn2+. Nothing exciting happens (no reaction). Then, dip a piece of zinc metal into a solution of Cu2+. Zinc reduces the Cu2+ ions and copper metal plates onto the zinc.

Or, we could rely on tables of standard reduction potentials for half cells, measured against the standard hydrogen electrode SHE (for which E is defined to be ZERO). Standard reduction potentials come from Wikipedia , which mines them from a number of legitimate sources.

SHE:
$$\ceH2(1 atm) + 2e- -> 2H+(1 M) \ \ \ E^o =0 \text V$$
For zinc:
$$\ceZn->Zn^2+ \ce+ 2e- \ \ \ E^o=-0.762 \text V$$
For copper:
$$\ceCu->Cu^2+ \ce+ 2e- \ \ \ E^o =+0.34 \text V$$
To generate a spontaneous reaction, these half cells are combined in such a way so that the overall cell potential is positive:
$$\ceZn->Zn^2+ \ce+ 2e- \ \ \ E^o=+0.762 \text V+$$
$$\ceCu^2+ \ce+ 2e- -> Cu(s) \ \ \ E^o=+0.34 \text V$$
$$\ceZn(s) + Cu^2+ (aq) \ce-> Zn^2+ (aq)\ce + Cu(s)\ \ E^o=+1.10 \text V$$
This analysis only applies to standard conditions. Under nonstandard conditions (for example [Zn2+]>>[Cu2+], then the reverse reaction could be spontaneous.

edited Nov 1 ’17 at 11:07

Felipe S. S. Schneider

1,98421129

answered Nov 22 ’12 at 2:16

Ben Norris

34k779144

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1
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The answer by Ben Norris is nice but it seems to have an additional confusion. The difference between reduction potentials of copper and zinc can be calculated based on the empirical ionization data that Ben describes, but this doesn’t mean that the difference has nothing to do the electronegativity of the two different elements. A nice discussion of this issue is provided at the following link .

edited Jul 6 ’15 at 20:10

M.A.R. ಠ_ಠ

6,824134978

answered Jan 1 ’14 at 17:45

NotAnExpert

111

• Could you try to elaborate on this; maybe paraphrasing/summarizing the link here?
–  ManishEarth
Jan 1 ’14 at 18:04

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0
down vote

Electronegativity is tendency of an atom or a functional group to attract electrons (or electron density) towards itself. Adding an electron to copper is very easy because of its valence orbital which has one free electron, which wants to pair with another electron, whereas in zinc, the valence shell is completely filled, i.e., d-orbital.

Config of Cu: Ar 4s2, 3d9

Config of Zn: Ar 4s2 3d10

edited Oct 31 ’17 at 17:36

jerepierre

9,29032446

answered Oct 31 ’17 at 17:23

Mcenroe Ng

11

## Not the answer you’re looking for? Browse other questions tagged physical-chemistry electrochemistry or ask your own question .

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