What is the Difference Between Effective Nuclear Charge and Shielding Effect?
🆚 Go to Comparative Table 🆚The effective nuclear charge (Zeff) and the shielding effect are related concepts in atomic physics and chemistry. Here are the main differences between the two:
- Effective Nuclear Charge (Zeff): This is the net positive charge experienced by an electron in a multi-electron atom. The term "effective" is used because the shielding effect of negatively charged electrons prevents higher orbital electrons from experiencing the full nuclear charge. The effective nuclear charge can be calculated using the formula: $$Z_{eff} = Z - S$$, where Z is the atomic number (number of protons in the nucleus) and S is the shielding constant.
- Shielding Effect: This refers to the core electrons repelling the outer electrons, which lowers the effective charge of the nucleus on the outer electrons. The shielding effect is responsible for reducing the nuclear charge experienced by electrons in higher orbitals. It is also responsible for the variation in atomic radii across the periodic table.
In summary, the effective nuclear charge (Zeff) is the net positive charge experienced by an electron in a multi-electron atom, while the shielding effect is the reduction of the attraction force between electrons and the atomic nucleus in an atom. The shielding effect influences the effective nuclear charge and serves to weaken the attractive forces between electrons and the nucleus as a function of the electron's distance from the nucleus.
Comparative Table: Effective Nuclear Charge vs Shielding Effect
The difference between effective nuclear charge and shielding effect can be summarized in the following table:
| Property | Effective Nuclear Charge | Shielding Effect |
|---|---|---|
| Definition | The actual amount of positive charge experienced by an electron in a multi-electron atom. | The reduction of the attraction force between electrons and the atomic nucleus due to the presence of inner-shell electrons. |
| Symbol | Zeff | S |
| Calculation | Zeff = Z - S, where Z is the atomic number (number of protons in the nucleus) and S is the shielding constant. | There is no specific mathematical formula for calculating the shielding effect, as it is a qualitative concept. |
| Significance | Explains atomic properties like atomic size, ionization energy, and electronegativity. | Describes the repulsion of outer electrons by inner electrons, which leads to a decrease in the effective nuclear charge experienced by outer electrons. |
| Dependence | Depends on the number of electrons and protons. | Depends on the number of electrons. |
The effective nuclear charge is a measure of the net positive charge experienced by an electron in an atom, while the shielding effect is the reduction of the effective nuclear charge experienced by an outer electron due to the presence of inner-shell electrons. The shielding effect is caused by the combination of partial neutralization of nuclear charge by core electrons and by electron-electron repulsion.
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