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DIPOLE MOMENT. Electronegativity Polarity of Bonds Dipole Moment Dipole Moment of Polar Covalent Bond Dipole Moment of Non Polar Covalent Bond Example of Dipole Moment. Next. ELECTRONEGATIVITY.

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DIPOLE MOMENT

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DIPOLE MOMENT

Electronegativity

Polarity of Bonds

Dipole Moment

Dipole Moment of Polar Covalent Bond

Dipole Moment of Non Polar Covalent Bond

Example of Dipole Moment

Next


ELECTRONEGATIVITY

Definition: Electronegativity is chemical property that describes the ability of an atom to attract electron towards itself in a covalent bond.

Symbol: “X”

Trends In Electronegativity:

Electronegativity increases across the period.

Decrease down the group.

Fluorine is most electronegative element.

Cesium is least electronegative element.

Exceptions: Gallium and Germanium have higher electronegative than Aluminum and Silicon respectively because of the D-block contradiction.

Order In Decreasing Electronegativity:

F>O>N>Br>I>P>H>Si


BondPolarity

Definition: When there is a bond between atom with (difference< 1.7) different electronegativity , then more electronegative atoms has a partial negative charge, and other has a partial positive charge, resulting a formation of Polar Covalent Bond.

Polar Molecules: A molecule is polar when their exists two separate poles of charges in the molecules at two different positions.

Example of Polar Molecules: H2O, HCL, NH3,SO2 etc.

Non –Polar Molecules: Those molecules in which there is no charge separation of positive and negative charges in a molecule and such a resultant molecule is neutral.

Example of Non Polar Molecules: Co2, BF3, BeH2, CH4 etc.


Dipole Moment

  • Definition: Dipole Moment refers to the quality of a system to behave like a dipole. It is defined as the product of the magnitude of charge on atoms and the distancebetween two bonded atoms.

  • Its common unit is Debye and SI unit is coulomb meter.

  • Formula: ц = Q * R, where Q is charge and R is distance between two bonded atoms.

  • It is a vector Quantity and its direction is given by an arrow pointing from positive to negative centers.

  • 1 Debye = 3.33564 * 10^-30 coulomb meters

  • Greater the charge larger will be the dipole moment

  • Smaller the distance lesser will be the dipole moment


Dipole Moment of Polar Covalent Bond

When a bond is formed between two dis-similar atoms, then more electronegative element becomes more electron rich whereas the less electronegative element becomes electron deficient, resulting a polar Covalent Bond.

The dipole moment of polar bond is non-zero and is represented as Цbond ≠ 0

The dipole moment of polar molecules is non- zero.


Dipole Moment of Non-PolarCovalent Bond

When a bond id formed between two similar atoms with similar electronegativity, then bond pair of electrons is equally attracted by both the atoms. As e result both the atoms are neutral.Such a bond formed is Non-Polar Covalent Bond.

The dipole moment id non- polar bond is zero and is represented as

цbond =0.

The resultant dipole moment of a non- polar molecule is zero and is represented as цmolecule =0.


Example of Dipole Moment

H2O (Water): In Case of water, there are two bonds each one is polar. We can get the resultant of both O-H bonds is in upward direction by adding vector ally. Additionally, the one pairs increase the molecular dipole since they consists of significant negative ion construction. So we call water a polar molecule because it has a molecular dipole.

BeCl2: In Case of BeCl2, two polar bonds at 180 degree from each other and of the same magnitude. Thus, they cancel each other. So molecule is non- polar even though the bond is polar.

BF3: In BF3, three bond dipoles and each at 120 degree from each other. These add vectorially in such a way as to cancel each other out. So, the molecule is non- polar.

CH4: In Methane molecule, there are 4- polar bonds oriented at the tetrahedral angle of 109.5 degree from each other and these form bond dipoles cancel out each other. So this molecule is non- polar.

PCL5: In Phosphorus pentachloride, the 3 equatorial bond cancels out each other dipole moment and axial bonds are at 180 degree to each other and cancel Out. So, molecule is non- polar.


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