Questions on Electron Shielding
Multiple-Choice Questions: Electron Shielding
🔹 Basic Concepts
1. What is electron shielding?
A) The attraction between nucleus and valence electrons
B) The repulsion between protons and neutrons
C) The blocking of attraction between nucleus and outer electrons by inner electrons
D) The emission of electrons from metal surfaces
E) The binding of electrons to an atom
2. Which electrons are primarily responsible for shielding?
A) Valence electrons
B) Electrons in the highest energy level
C) Protons
D) Inner (core) electrons
E) Neutrons
3. As electron shielding increases, effective nuclear charge (Zₑff) generally:
A) Increases
B) Decreases
C) Remains constant
D) Equals atomic number
E) Doubles
4. Why does shielding cause a decrease in ionization energy down a group?
A) Valence electrons are more strongly attracted
B) The number of protons decreases
C) Inner electrons block nuclear attraction
D) Electron affinity increases
E) Neutrons shield the valence shell
5. Which of the following best describes the shielding effect?
A) Core electrons attract valence electrons
B) Valence electrons block nuclear charge
C) Inner electrons reduce the nuclear pull felt by valence electrons
D) Electrons shield each other equally
E) Electrons neutralize the charge of the nucleus
🔹 Trends and Relationships
6. As atomic number increases within a group, shielding effect:
A) Increases
B) Decreases
C) Remains the same
D) Disappears
E) Is unpredictable
7. Which element experiences the greatest electron shielding?
A) Lithium
B) Fluorine
C) Cesium
D) Neon
E) Oxygen
8. What is the effect of increased shielding on atomic radius?
A) Radius decreases
B) Radius stays the same
C) Radius increases
D) Radius becomes zero
E) No effect
9. Why is potassium larger in size than sodium?
A) It has more valence electrons
B) Less proton attraction
C) More inner electron shells, increasing shielding
D) It has a smaller atomic mass
E) It has fewer protons
10. Which has the least shielding effect?
A) Hydrogen
B) Beryllium
C) Boron
D) Carbon
E) Lithium
🔹 Applications
11. Which of the following affects the strength of shielding most?
A) Valence electron configuration
B) Number of protons
C) Number of core electrons
D) Mass number
E) Type of chemical bond
12. Which group has the greatest shielding effect overall?
A) Group 1 (alkali metals)
B) Group 17 (halogens)
C) Group 2 (alkaline earth metals)
D) Group 18 (noble gases)
E) Transition metals
13. Which element has the weakest effective nuclear charge due to shielding?
A) Francium
B) Lithium
C) Beryllium
D) Neon
E) Nitrogen
14. Shielding makes it easier to:
A) Gain electrons
B) Ionize inner electrons
C) Remove valence electrons
D) Reduce electronegativity
E) Decrease neutron number
15. The difference between atomic number and effective nuclear charge is largely due to:
A) Ionization energy
B) Shielding by inner electrons
C) Neutron deficiency
D) Covalent radius
E) Melting point
🔹 Higher-Order Thinking
16. Which pair of elements demonstrates increased shielding from top to bottom in a group?
A) Carbon and Oxygen
B) Lithium and Fluorine
C) Fluorine and Chlorine
D) Sodium and Aluminum
E) Nitrogen and Neon
17. Why do electrons in the same energy level not shield each other effectively?
A) They are repelled by protons
B) They are farther from the nucleus
C) They do not lie between each other and the nucleus
D) They are unstable
E) They move too quickly
18. Which statement about shielding and ionization energy is correct?
A) Higher shielding increases ionization energy
B) Shielding only affects d- and f-block elements
C) Shielding reduces the energy required to remove an electron
D) Shielding has no effect on periodic trends
E) Shielding increases nuclear charge
19. Why is helium less shielded than neon?
A) Helium is larger
B) Helium has more inner electrons
C) Helium has no inner electron shells
D) Neon has fewer protons
E) Neon is radioactive
20. Which of the following increases the shielding effect in atoms?
A) Increasing valence electrons only
B) Adding protons only
C) Adding electrons to inner shells
D) Removing electrons from outer shell
E) Increasing electronegativity
Answers with Explanations
1. C – Electron shielding is the reduction of the attractive force between nucleus and outer electrons due to repulsion by inner electrons.
2. D – Inner (core) electrons shield outer electrons from the full force of the nucleus.
3. B – Increased shielding reduces the effective nuclear charge felt by valence electrons.
4. C – More inner shells down a group lead to greater shielding, making it easier to remove outer electrons.
5. C – Inner electrons reduce the nuclear pull felt by the valence electrons, weakening the attraction.
6. A – More electron shells mean more shielding as you move down a group.
7. C – Cesium has the most energy levels and inner electrons, so experiences the greatest shielding.
8. C – Shielding reduces nuclear pull, allowing outer electrons to be farther away, increasing atomic radius.
9. C – Potassium has more energy levels than sodium, increasing shielding and atomic size.
10. A – Hydrogen has only one electron and no inner shells, so no shielding effect.
11. C – The number of core (inner) electrons determines the strength of the shielding effect.
12. A – Alkali metals have large atomic sizes and many inner electrons, leading to strong shielding.
13. A – Francium, as a heavy alkali metal, has many inner electrons and weak effective nuclear charge.
14. C – Shielding weakens nuclear attraction, making it easier to remove outer (valence) electrons.
15. B – Inner electrons reduce the effective nuclear charge experienced by outer electrons.
16. C – Chlorine is below fluorine in Group 17 and has more inner electrons, so more shielding.
17. C – Electrons in the same shell do not lie between each other and the nucleus, so can't shield well.
18. C – Greater shielding means electrons are less tightly held, lowering ionization energy.
19. C – Helium has only one shell, so no inner electrons to cause shielding.
20. C – Adding electrons to inner shells increases shielding since they can block nuclear pull.
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