charge transfer electron transfer charge transfer by induction charge transfer by conduction charge transfer by friction

2. Charge Transfer Process In The
Absence Or Presence Of Electric
Field
Electrochemistry
Presented To Dr:Muhammad Afzal
Presented By: Tayyaba khalid 013 (B.s 15 )
Chemistry Department
Sbbu sba
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3. Terminology
• Charge transfer
• Electric field
• CHARGE TRANSFER
• A charge-transfer is an association of two or more molecules, or
of different parts of one large molecule, in which a fraction of
electronic charge is transferred between the molecular entities.
• Electric Field
• A region around a charged particle or object within which a
force would be exerted on other charged particles or objects
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4. What Does Charge Transfer Mean
• Usually charge refers the charge of electron,
which is being transferred
within the molecular entity .
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5. Transferring charge
• An object become charged only when electrons are
transferred from one location to another. Charges are
neither created nor destroyed. This is a rule known as the
law of conservation of charge .If one object gives up
electrons, another object gains those electrons.
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6. • Why is this girl's hair standing straight up? She is
touching a device called a van de Graaff generator
The dome on top of the device has a negative electric
charge. When the girl places her hand on the dome,
she becomes negatively charged as well—right down
to the tip of each hair!
• Q: What causes the hair to stand on end?
A: All of the hairs have all become negatively charged,
and like charges repel each other. Therefore, the hairs
are pushing away from each other, causing them to
stand on end.
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7. • A Van de Graaff generator is an electrostatic
generator which uses a moving belt to accumulate electric
charge on a hollow metal globe on the top of an insulated
column, creating very high electric potentials. It produces
very high voltage direct current (DC) electricity at low current
levels. It was invented by American physicist Robert J. Van de
Graaff in 1929.Small Van de Graaff machines are produced
for entertainment, and education to teach
electrostatics larger ones are displayed in
some science museums.
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8. Transferring Electrons
• The girl pictured above became negatively charged because
electrons flowed from the van de Graaff generator to her.
Whenever electrons are transferred between objects, neutral
matter becomes charged. This occurs even with individual atoms.
Atoms are
neutral in electric charge because they have the
same number of negative electrons as positive
protons. However, if atoms lose or gain electrons
, they become charged particles called ions.
You can see how this happens in the Figure .
When an atom loses electrons, it becomes a positively
charged ion, or cation. When an atom gains electrons,
it becomes a negative charged ion, or anion.
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9. Conservation of Charge
•Conservation of Charge
• Like the formation of ions, the formation of charged matter
in general depends on the transfer of electrons, either
between two materials or within a material. However,
regardless of how electrons are transferred, the total charge
always remains the same. Electrons move, but they aren’t
destroyed. This is the law of conservation of charge.
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10. • There are two methods through which charge transfer can take place
between two bodies.
• Charging by Conduction
• Charging by Induction
• Charge transfer by Conduction
• Charge transfer by conduction using a negatively charged object
• As we know like charges repel each other and spread about as far as
possible in order to reduce this repulsion. In doing so, the electrons
(negatively charged) go to the extreme of the perimeter of the sphere
and if there is a pathway to another object where the electrons can
go, the electrons tend to move from one object to another. Let us
consider a negatively charged metal sphere. When the charged metal
sphere comes in contact with a neutral object, excess electrons from
the sphere move onto the neutral object and get spread evenly. As a
result of this process the object 2 acquires negative charge while the
metal sphere is still charged but has less number of electrons. This
process of charging by contact is termed as charging by conduction.
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12. • Charge transfer by conduction using a positively charged object
• As we know, a positively charged sphere has an excess of protons
which in other terms means a deficit of electrons. Let us consider two
objects one positively charged metal plate and a neutral metal sphere.
When a positively charged metal plate comes in contact with a neutral
metal sphere, the electrons from the neutral sphere get attracted
towards the positively charged metal plate. This process lasts until the
positive charge in the metal plate becomes redistributed. Having lost
electrons to the positively charged plate, the neutral sphere
experiences a deficit of electrons which makes it positively charged
while the positively charged metal plate is still charged but the deficit
of electron is comparatively less than before. This process of charge
transfer is defined as the charge transfer using a positively charged
object.
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13. In the above example we learnt about charge transfer
through the process of conduction using a positively or a
negatively charged object. Charge transfer can also take
place through the process of induction.
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14. • Charge transfer by Induction
• Charging by Induction: is the charging of a neutral object by bringing
another charged object close to; but not touching, the neutral object.
• Charging More Than One Object by Induction A positively charged
object can be used to induce a charge in a neutral object. You can also
use two objects at the same time to permanently charge the objects.
In sphere A, the electrons are attracted by the positive charge on the
balloon. The electrons the balloon draw electrons in sphere A to the
left side. The right side of the sphere becomes negatively charged.
Electrons in sphere B are attracted to sphere A and are transferred.
Keep the balloon in place and remove sphere B from sphere A, makes
sphere B permanently charged positively. Electrons are unable to move
back. Remove the balloon form sphere A allows the electrons to spread
throughout the sphere, yet it is still negatively charged
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15. • charge transfer by induction using a positively charged object
• In this section, we shall learn about the charge transfer through
the process of induction using a positively charged object. Taking
two spheres A and B, touching each other, as shown in the figure,
if we bring a positively charged balloon near sphere A, the
electrons from sphere B migrate towards sphere A due to the
attraction between opposite charges, thus leaving the sphere B
deficit of electrons. As a result, the sphere A gets negatively
charges and the sphere B gets positively charged. The spheres
are then separated using an insulating cover, a stand or gloves.
When the balloon is removed, the charges in sphere A and B
redistribute, spreading out evenly
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17. Rate Of An Electron Transfer Reaction
Under The Influence Of An Electric Field
• The Electric field is vector quantity directed normal to
interface.
• The electron transfer from the electrode to an electron
acceptor in solution is opposed by the field .when there is a
field across the interface the work done by the positive ion in
climbing the potential energy barrier has to include the
electrical work.in the presence of the field, the energies of all
the charged particles will be altered.
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18. Electron Transfer Reaction In The
Absence Of Electric Field
• Consider the movement of positive ion from the solution side
of the interface to metal surface .somewhere along the way
the electron transfer occurs from electrode to ion. The
positive ion to have a certain activation energy before the
charge transfer reaction is accomplished .
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