Presentation Transcript

1. Effective Nuclear Charge

   Weston Conner
2. Background Knowledge Outer electrons are attracted to the nucleus. Coulomb’s law of attraction indicates that the strength of the interaction between two electrical charges depends on the magnitude of the charges and the distance between them
3. Background Knowledge This means the force of attraction between the nucleus and an electron depends on the strength of the net nuclear charge affecting the electron and the average distance between the electron and the nucleus. Force of attraction rises as nuclear charge rises Force of attraction decreases as the electron moves away from the nucleus
4. Background Knowledge In general, there are so many electrons repelling each other; that one cannot examine the situation realistically. The energy of each electron can be estimated based on the average conditions created by the nucleus and other electrons. The electrons can be treated individually, as if they were in an electric field created by the nucleus and other electrons
5. Effective Nuclear Charge This electric field is similar to one created by a charge located at the nucleus—called the effective nuclear charge.
6. Effective Nuclear Charge Zeff stands for effective nuclear charge The Zeff acting on an electron is equal to the protons in the nucleus, Z, minus the average number of electrons, S. Zeff= Z — S
7. Effective Nuclear Charge Electron density between the nucleus and outer electrons decreases the Zeffacting on the outer electrons. They inner electrons are said to “shield” the outer electrons.
8. Zeff and the Periodic Table The Zeff felt by outer electrons increases as one moves from element to element across any row on the periodic table The Zefffelt by outer electrons hardly changes as one goes down a family.