Elektronegativität

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Elektronegativität (abbreviation EN; Symbol <math> \ chi< /math>) is a relative measure for the ability of an atom to actually draw in a chemical connection the connection electrons. It is determined among other things by the nuclear charge and the atomic radius (explanations concerning the connections are in the sections of the individual scales to reread). The Elektronegativität can be taken therefore as reference point for the polarity and the electrovalence character of a connection: The more highly the difference in the Elektronegativität of the bound elements, the more polar is the connection.

Atoms with high Elektronegativität one calls also electronegative, such with small Elektronegativität as electricalpositive. The Elektronegativität takes i.d.R. within one element period from left to right too, and within a group of elements from bottom to top too.


Table of contents

mapping systems

the Elektronegativitäts model was introduced 1932 by Linus Pauling and refined later several times. Today also the scales of Allred Rochow and Mulliken use find beside the Pauling scale.


Allred Rochow scale

the Elektronegativität after A. L. Alltalk and E. G. Rochow becomes often also with <math> c_ {ACRE}< /math> or <math> \ chi_ {ACRE}< /math> designated.

The scale is based on the consideration that the Elektronegativität proportionally to electrostatic attraction the F, which exercises the nuclear charge Z on the Bindungselektronen (of internal electrons shielded), is:

<math> F \ propto \ frac {e^2 \ cdot Z_ {\ rm EFF}} {r^2}< /math>

whereby r the atomic radius, e the elementary charge and <math> Z_ {\ rm EFF}< /math> the effective nuclear charge number is.


table of the values after Allred Rochow



Group 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
period
1 H
2.20
He
5.20
2 left
0,97

1.47
B
2.01
C
2.50
N
3.07
O
3.50
F
4.10
Ne
4,50
3 well
1.01
mg
1.23
aluminium
1.47
SI
1.74
P
2.06
S
2.44
Cl
2.83
acre
3,20
4 K
0,91
approx.
1.04
sports club
1.20
Ti
1.32
V
1.45
CR
1.56
Mn
1.60
Fe
1.64
CO
Never
1,70
1.75
cu
1.75
Zn
1.66
Ga
1.82
Ge
2.02
As
2.20
SE
2.48
Br
2.74
Kr
2.90
5 Rb
0.89
SR
0.99
Y
1.11
Zr
1.22
Nb
1.23
Mo
1.30
Tc
1.36
Ru
1.42
RH
1.45
Pd
1.30
AG
1.42
CD
1,46
in
1.49
SN
1.72
self-service
1.82
width unit
2.01
I
2.21
Xe
2,40
6 Cs
0.86
Ba
0.97
La
Hf
1.23
TA
1.33
W
1.40
RH
1.46
OS
1.52
IR
1.55
Pt
1,42
outer ones
1.42
Hg
1.44
tl
1.44
Pb
1.55
Bi
1.67
Po
1.76
RKs
1.96
Rn
2,10
7 Fr
0.86
RA
0.97
AC
Rf
railways
Sg
Bh
Hs
Mt
DS
Rg
Uub
Uut
Uuq
Uup
Uuh
Uus
Uuo

</center> Allred Rochow values of the Elektronegativität in the periodic system of the elements

Mulliken scale

in the Mulliken scale (1934 by Robert S. Mulliken suggested) becomes the Elektronegativität as average value from that ionization energy <math> E_I< /math> and the electron affinity <math> E_ {\ rm I/O}< /math> (electron affinity) computes:

<math> \ chi_ {\ rm M} = \ frac {E_ {\ rm I/O} +E_I} {2}< /math>

This energy is indicated in electronvolts.


table of the values after Mulliken



Group 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
period
1 H
3.06
He
2 left
1,28

1.99
B
1.83
C
2.67
N
3.08
O
3.21
F
4.42
Ne
4,60
3 well
1.21
mg
1.63
aluminium
1.37
SI
2.03
P
2.39
S
2.65
Cl
3.54
acre
3,36
4 K
1,03
approx.
1.30
sports club
Ti
V
CR
Mn
Fe
CO
Never
Cu
Zn
Ga
1.34
Ge
1.95
As
2.26
SE
2.51
Br
3.24
Kr
2.98
5 Rb
0.99
SR
1.21
Y
Zr
Nb
Mo
Tc
Ru
RH
Pd
AG
CD
In
SN
1.83
self-service
Width unit
2.34
I
2.88
Xe
2,59
6 Cs
Ba
La
Hf
TA
W
RH
OS
IR
Pt
Outer one
Hg
tl
Pb
Bi
Po
RK
Rn
7 Fr
RA
AC
Rf
railways
Sg
Bh
Hs
Mt
DS
Rg
Uub
Uut
Uuq
Uup
Uuh
Uus
Uuo

</center>

Pauling scale

the Pauling model is based on the Elektronegativitäts difference of two atoms A and B as measure for the ionischen portion of its connection of A-B. It presupposes the knowledge of the experimentally determined connection dissociation energies of the molecules of A-B, A 2 and B 2 .

The Elektronegativitätsdifferenz of two atoms A and B results in accordance with:

<math> D_ {OFF} - \ {D_ sqrt {AA} D_ {BB}} = 96 {,} 48~ \ frac {\ rm kJ} {\ rm mol} (\ chi_A \ chi_B) ^2< /math>

The computation of the dimensionless Elektronegativitätswerte of the chemical elements from the difference the value became math \ <chi_F> = 3 {,} 98 /math for< Fluor> as point of reference fixed.


In the literature often different values for the EN are after Pauling, which is to due to the following reasons:

    • The connection dissociation energies are for some elements and/or. Connections experimentally with difficulty accessible.
    • Reference values used in former times were <math> \ chi_F = 4 {,} 00< /math> and <math> \ chi_H = 0 {,} 00< /math> (original value for hydrogen).
    • Instead of the geometrical means <math> \ {D_ sqrt {AA} D_ {BB}}< /math> became in former times also the arithmetic means <math> \ frac {D_ {AA} +D_ {BB}} {2}< /math> used.
    • Finally different values for the porportionality factor are in the literature.


table of the values after Pauling

Characteristics of the atoms of the main groups in the periodic system (from left to right)

=> Atomic radius takes off
=> Ionization energy too
=> Elektronegativität increases

Group 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
period
1 H
2.1
He
2 left
1,0

1.5
B
2.0
C
2.5
N
3.0
O
3.5
F
4.0
Ne
3 well
0.9
mg
1.2
aluminium
1.5
SI
1.8
P
2.1
S
2.5
Cl
3.0
acre
4 K
0,8
approx.
1.0
sports club
1.3
Ti
1.5
V
1.6
CR
1.6
Mn
1.5
Fe
1.8
CO
1,9
never
1.8
cu
1.9
Zn
1.6
Ga
1.6
Ge
1.8
As
2.0
SE
2.4
Br
3.0
Kr
5 Rb
0.8
SR
1.0
Y
1.2
Zr
1.4
Nb
1.6
Mo
1.8
Tc
1.9
Ru
2.2
RH
2.2
Pd
2.2
AG
1.9
CD
1,7
in
1.7
SN
1.8
self-service
1.9
width unit
2.1
I
2.5
Xe
6 Cs
0.7
Ba
0.9
La
Hf
1.3
TA
1.5
W
1.7
RH
1.9
OS
2.2
IR
2.2
Pt
2,2
outer ones
2.4
Hg
1.9
tl
1.8
Pb
1.9
Bi
1.9
Po
2.0
RKs
2.2
Rn
7 Fr
0.7
RA
0.9
AC
Rf
railways
Sg
Bh
Hs
Mt
DS
Rg
Uub
Uut
Uuq
Uup
Uuh
Uus
Uuo
Lanthanoide *
La
1.1
Ce
1.12
Pr
1.13
lp
1.14
Pm
1.13
Sm
1.17
European Union
1.2
Gd
1.2
Tb
1.1
Dy
1.22
Ho
1.23
it
1.24
TM
1.25
Yb
1.1
Lu
1.27
Actinoide **
AC
1.1
Th
1.3
Pa
1.5
U
1.38
NP
1.36
Pu
1.28
to
1,13
cm
1.28
UC
1.3
Cf
1.3
it
1.3
FM
1.3
MD
1.3
NO
1.3
Lr
1.3

< /center> Pauling values of the Elektronegativität in the periodic system of the elements

other Elektronegativitäts scales

after L.C. All the Elektronegativität from the energy state of the bonding electrons is computed, what permits a spectroscopic regulation.

R. T. Sanderson leads the Elektronegativität as alltalks & Rochow on the effective nuclear charge back.

literature

  • L. Pauling, The Nature OF the Chemical bond, Cornell Univ., the USA, 3rd OD., 1960.
  • R. S. Mulliken, J. Chem. one. Physical one, 1934, 2, 782.
  • A. L. Alltalk, J. Inorg. Nucl. Chem. one, 1961, 17, 215.
  • A. L. Alltalk and E.G. Rochow, J. Inorg. Nucl. Chem. one, 1958, 5, 264.
  • R. T. Sanderson, J. Chem. one. OD., 1988, 65, 112.
  • L. C. Everything, J. To. Chem. one. Soc., 1989, 111, 9003.

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