Electronegativity of The Periodic Trends
Electronegativity is a measure of the ability of an atom or molecule to attract electron pairs in the context of chemical bonds.Electronegativity can not be calculated directly, but must be calculated from the properties of atoms and molecules. Several methods of calculation have been proposed. Although in every method there is little difference in the numerical value of the electronegativity, all methods have the same trend in the period between the elements.The most commonly used method is the method of Pauling. The results of this calculation produces a dimensionless value and is usually referred to as the Pauling scale relative scale that ranged from 0.7 to 4.0 (hydrogen = 2.2). When other methods of calculation is used, there is a convention (although not required) to use the same scale range Pauling scale: this is known as an electronegativity in Pauling units.
Electronegativity is not part of the nature
of the atom, but only the nature of atoms in molecules. Properties of single
atoms is equal to the electron affinity electronegativity. Electronegativity in
an element will vary depending on the chemical environment, but it is usually
regarded as a property of displaced, an electronegativity value is considered
to apply to various situations vary.
Carbon-fluorine
bond
Fluorine is much more electronegative than
carbon. Original value Pauling scale is
carbon
|
2.5
|
fluorine
|
4.0
|
This means that the fluorine attract
electrons more strongly than carbon. Ties on average will look like this:
Carbon-chlorine
bond
Its electronegativity is:
carbon
|
2.5
|
chlorine
|
3.0
|
Pair bonding electrons will be drawn to
chlorine but not as strong as in florins. Because chlorine is not senegatif
florins.
Bond
polarity and inductive effects
Polarity bond
Think about the carbon-fluorine bond again.
Because the bonding pair of electrons pulled towards the side of the florin
would be more negative. While the pair of carbon becomes slightly more electron
deficiency and be more positive.
symbols + and - means "more
positive" and "more negative". + Read with the "delta
plus" or "positive delta".
We describe a bond that has the more negative
and more positive as polar.
Inductive effect
A fluorine atom as to attract the electron
pair bond is said to have a negative inductive effect.
Most of the atoms that you would have
encountered mostly have negative inductive effect when bonded to carbon because
they are more electronegative than carbon.
You will also find some group of atoms
that has little inductive effect posotif. They push the electrons to the carbon
they are bonded and makes it more negative.
Inductive effects are often given the symbol:
I-(negative inductive effect) and + I (positive inductive effect).
Some important examples of polar
bonds
Hydrogen Bromide (and other hydrogen halides)
Bromine (halogen and others) are all more
electronegative than hydrogen halide and all hydrogen bonds have polar bonds
with the hydrogen halides are more positive and more negative parts.
The polarity of these molecules is crucial as
they react with alkenes.
Carbon-bromine bond in Halogenoalkena
Bromine is more electronegative than carbon
that bonds polarized as we have language support in CF and C-l.
The polarity of the carbon-halogen important
in halogenoalkanes reaction.
Carbon-oxygen
bond
A model orbital of the C = O at methanal,
CHCHO, looks like this:
4 komentar
Write komentarIn electronegativity, the most commonly used method is the method of Pauling. Methods Pauling stated that results of this calculation, resulting in electronegativity values ranged from 0.7 to 4.0? Why are worth only ranged between 0.7 to 4.0, why is the value not more or less?
ReplyThe method commonly used is the method of Pauling. The results of this calculation produces a dimensionless value and is usually referred to as the Pauling scale relative scale that ranged from 0.7 to 4.0 (hydrogen = 2.2). When other methods of calculation is used, there is a convention (although not required) to use the same scale range Pauling scale: this is known as an electronegativity in Pauling units Pauling.dan using tally between the range of 0.7 to 4.0 is under consideration, if it created a new calculation, it will be more difficult to calculate
Replybecause the elements found today still has a maximum and minimum limit of electronegativity as Fluorine (the most electronegative element) has a value of 4.0, the value is down to cesium and francium lowest electronegative 0.7.
ReplyPauling method is the method most commonly used, and this method has provisions electronegativity value of 0.7 to 4. if you use a value other than that it will be difficult to quantify.
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