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Chapter 7: Problem 74

What is meant by the term "shielding of electrons" in an atom? Using the \(\mathrm{Li}\) atom as an example, describe the effect of shielding on the energy of electrons in an atom.

Short Answer

Expert verified
The term 'shielding of electrons' refers to the protection of valence electrons from the attractive force of the nucleus by the inner or core electrons. In a Lithium atom, the two core electrons in the K shell shield the valence electron in the L shell from the full charge of the nucleus. This reduces the pull on the valence electron, hence requires less energy to remove it. The shielding effect therefore results in a larger atomic size and reduced ionization energy or electron affinity.

Step by step solution

01

Understanding the Shielding Effect

Shielding effect describes how the core (inner) electrons protect or 'shield' the outermost or valence electrons from the attractive force of the positive nucleus. This is because the inner electrons are closer to the nucleus and experience a stronger electromagnetic force, thereby diminishing the pull of the nucleus on the valence electrons.
02

Applying the Concept to the Lithium Atom

A Lithium atom (Li) is used as an example here. It has three electrons; two are core electrons that occupy the first energy level (K shell), while the other is a valence electron in the second energy level (L shell). Due to the shielding effect, these core electrons shield the valence electron from the nuclear charge i.e., they effectively reduce the force of attraction exerted by the positive nucleus on the valence electron.
03

Effect on the Energy of Electrons

The effect of the shielding can be explained in the context of energy levels of the electron. Electrons closer to the nucleus are at lower energy levels while those further away are at higher energy levels. Because of the shielding effect, the valence electrons of lithium experience less pull from the nucleus. This means that less energy is required to remove a valence electron from lithium than if the shielding effect did not exist, hence affecting the ionization energy of the atom. As a result, shielding increases the atomic size and decreases ionization energy and electron affinity.

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Most popular questions from this chapter

Indicate the number of unpaired electrons present in each of the following atoms: \(\mathrm{B}, \mathrm{Ne}, \mathrm{P}, \mathrm{Sc}, \mathrm{Mn}, \mathrm{Se},\) \(\mathrm{Kr}, \mathrm{Fe}, \mathrm{Cd}, \mathrm{I}, \mathrm{Pb}\).

Which of the following species has the most unpaired electrons? \(\mathrm{S}^{+}, \mathrm{S},\) or \(\mathrm{S}^{-}\). Explain how you arrive at your answer.

Why do the \(3 s, 3 p,\) and \(3 d\) orbitals have the same energy in a hydrogen atom but different energies in a many-electron atom?

Give two everyday examples that illustrate the concept of quantization.

What is the maximum number of electrons in an atom that can have the following quantum numbers? Specify the orbitals in which the electrons would be found. (a) \(n=2, m_{s}=+\frac{1}{2} ;\) (b) \(n=4, m_{\ell}=+1\) (c) \(n=3, \ell=2 ;\) (d) \(n=2, \ell=0, m_{s}=-\frac{1}{2} ;\) (e) \(n=4\) ,\(\ell=3, m_{\ell}=-2\)
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