Can someone explain this to me please? I have a problem understanding effective nuclear charge (Zeff), more specifically.
Thank you!!!
Thank you!!!
coulomb's law
- Thread starter mashinka
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Ok! First let's see what the Coulomb's Law states:
The magnitude of the electrostatic charge between two charged bodies is directly proportional to the products of the magnitudes of the two charges and inversely proportional to the square of the distance between the two charges. So:
F = Ke (q1*q2)/r^2
The effective nuclear charge is the net positive charge that is experienced by an electron.
Where do we see this in nature?
Well, how about the electrostatic force between an electron and the nucleus of an atom?
If there's only one electron orbiting the nucleus, the effective nuclear charge can be calculated using the Coulomb's law (Think about it: You know the magnitude of the charge of the electron (q1), Ke is constant, provided that you have F and r, you can then measure (q2) or the net positive charge that is experienced by the electron from the nucleus).
However, if there are more electrons orbiting the nucleus, the above formula can no longer be used to calculate the effective nuclear charge. Why?
Consider an atom that has multiple electrons orbiting in the nucleus. These electrons are distributed within different energy levels surrounding the nucleus. Under such circumstances, the electrons that are distributed within the inner energy levels prevent the electrons on the outer energy levels to experience the full attractive force of the nucleus. This is known as the shielding effect. It's like building a wall of electrons between the nucleus and the electron within the outer energy level, which diminishes the full attractive force of the nucleus on that electron.
Under such circumstances the effective nuclear charge must be calculated via the following formula to account for the shielding effect:
Zeff = Z - S
Z-->Number of protons within the nucleus
S-->Average number of electrons between the nucleus and the outer electron.
The magnitude of the electrostatic charge between two charged bodies is directly proportional to the products of the magnitudes of the two charges and inversely proportional to the square of the distance between the two charges. So:
F = Ke (q1*q2)/r^2
The effective nuclear charge is the net positive charge that is experienced by an electron.
Where do we see this in nature?
Well, how about the electrostatic force between an electron and the nucleus of an atom?
If there's only one electron orbiting the nucleus, the effective nuclear charge can be calculated using the Coulomb's law (Think about it: You know the magnitude of the charge of the electron (q1), Ke is constant, provided that you have F and r, you can then measure (q2) or the net positive charge that is experienced by the electron from the nucleus).
However, if there are more electrons orbiting the nucleus, the above formula can no longer be used to calculate the effective nuclear charge. Why?
Consider an atom that has multiple electrons orbiting in the nucleus. These electrons are distributed within different energy levels surrounding the nucleus. Under such circumstances, the electrons that are distributed within the inner energy levels prevent the electrons on the outer energy levels to experience the full attractive force of the nucleus. This is known as the shielding effect. It's like building a wall of electrons between the nucleus and the electron within the outer energy level, which diminishes the full attractive force of the nucleus on that electron.
Under such circumstances the effective nuclear charge must be calculated via the following formula to account for the shielding effect:
Zeff = Z - S
Z-->Number of protons within the nucleus
S-->Average number of electrons between the nucleus and the outer electron.
ok, so in the case of more than one electron Zeff takes the place of just q1? And if so, then would be just calculate q2 according to the number of protons that are present?
Thanks for the help!
Thanks for the help!
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The number of protons really doesn't have anything to do with the Coulomb's law. It has to do with q1 & q2, which are the magnitude of the charged bodies (electrons and protons) rather than their number!
