Questions on Electron Affinity
Multiple-Choice Questions: Electron Affinity
🔹 Basic Concepts
1. What is electron affinity?
A) Energy required to remove an electron from a gaseous atom
B) Energy released when a gaseous atom gains an electron
C) Energy used to excite an electron to a higher orbital
D) Energy needed to form an ionic bond
E) Energy stored in chemical bonds
2. Which group on the periodic table has the highest (most negative) electron affinity?
A) Group 1 (alkali metals)
B) Group 2 (alkaline earth metals)
C) Group 17 (halogens)
D) Group 18 (noble gases)
E) Group 3 (boron group)
3. What happens to electron affinity across a period from left to right?
A) It increases (becomes more negative)
B) It decreases (becomes more positive)
C) It remains constant
D) It first increases, then decreases
E) It fluctuates randomly
4. Which element is expected to have the lowest (least negative) electron affinity?
A) Fluorine
B) Oxygen
C) Sodium
D) Neon
E) Chlorine
5. Why do noble gases have nearly zero electron affinity?
A) They are radioactive
B) They have small atomic radii
C) They have full outer shells and resist adding electrons
D) Their nuclei are unstable
E) They have strong metallic bonds
🔹 Comparative Trends
6. Which of the following has the greatest electron affinity?
A) Oxygen
B) Sulfur
C) Fluorine
D) Chlorine
E) Bromine
7. Why is chlorine's electron affinity slightly greater than fluorine’s, even though fluorine is more electronegative?
A) Fluorine is heavier
B) Fluorine is smaller, causing more repulsion in the small orbital
C) Fluorine has more protons
D) Chlorine is a noble gas
E) Chlorine has a larger atomic radius and less repulsion
8. What is the general trend of electron affinity down a group?
A) Increases
B) Decreases
C) Stays constant
D) First decreases, then increases
E) Cannot be predicted
9. Which of these elements has the most positive (least exothermic) electron affinity?
A) Lithium
B) Beryllium
C) Boron
D) Nitrogen
E) Fluorine
10. Which of the following elements is most likely to form a stable anion?
A) Sodium
B) Magnesium
C) Fluorine
D) Neon
E) Aluminum
🔹 Electron Affinity and the Periodic Table
11. Which of the following elements releases the most energy when gaining an electron?
A) Carbon
B) Oxygen
C) Chlorine
D) Argon
E) Phosphorus
12. Electron affinity is measured in units of:
A) Kelvin
B) Grams
C) Joules or kJ/mol
D) Amperes
E) Seconds
13. Which group generally shows positive or near-zero electron affinity values?
A) Group 1
B) Group 17
C) Group 14
D) Group 18
E) Group 2
14. Why does nitrogen have a lower electron affinity than oxygen?
A) It has a full shell
B) Half-filled p orbitals cause extra repulsion
C) It has more shielding
D) It has more mass
E) Nitrogen is a metal
15. Electron affinity becomes more exothermic across a period due to:
A) Increased shielding
B) Decreased nuclear charge
C) Stronger attraction to added electrons
D) Decreased effective nuclear charge
E) More electron shells
🔹 Application and Analysis
16. Which process describes a negative electron affinity value?
A) Energy absorbed by the atom
B) No change in energy
C) Energy released when electron is added
D) Atom splitting into ions
E) Ionization energy calculation
17. Which of the following best explains why fluorine has a high electron affinity?
A) Fluorine is a noble gas
B) Fluorine has high ionization energy
C) Fluorine has a small atomic size and high effective nuclear charge
D) Fluorine has a full valence shell
E) Fluorine is a metal
18. Why do metals generally have low electron affinity?
A) Their valence shells are nearly full
B) They readily lose electrons
C) They have low melting points
D) They are noble gases
E) They are too electronegative
19. Which factor does NOT significantly affect electron affinity?
A) Atomic radius
B) Shielding effect
C) Nuclear charge
D) Ionization energy
E) Electron configuration
20. A high (very negative) electron affinity indicates:
A) The atom resists gaining electrons
B) The atom loses electrons easily
C) The atom releases a lot of energy when gaining an electron
D) The atom is a metal
E) The atom has low reactivity
Answers and Explanations
1. B – Electron affinity is the energy released when a gaseous atom gains an electron.
2. C – Halogens (Group 17) have the most negative electron affinity because they are one electron short of a full outer shell.
3. A – Electron affinity becomes more negative across a period due to increasing nuclear attraction.
4. D – Neon is a noble gas with a full outer shell and thus little tendency to gain electrons.
5. C – Noble gases have full valence shells and do not readily accept electrons.
6. D – Chlorine has the highest electron affinity (most negative value) among common elements.
7. B – Fluorine's very small size leads to electron-electron repulsion, slightly reducing the amount of energy released.
8. B – As atomic size increases down a group, the attraction for added electrons decreases, so electron affinity becomes less negative.
9. D – Nitrogen has a half-filled p orbital, making it less favorable to add an electron.
10. C – Fluorine has a high electron affinity and readily forms anions.
11. C – Chlorine releases the most energy when gaining an electron, due to its high effective nuclear charge.
12. C – Electron affinity is measured in joules (J) or kilojoules per mole (kJ/mol).
13. D – Noble gases (Group 18) have full outer shells and typically have zero or positive electron affinity.
14. B – Nitrogen’s half-filled p orbitals cause repulsion when an electron is added.
15. C – Greater nuclear attraction makes atoms more likely to accept electrons, releasing more energy.
16. C – Negative electron affinity values indicate that energy is released when an electron is added.
17. C – Fluorine’s small size and high nuclear charge make it strongly attract extra electrons.
18. B – Metals prefer to lose electrons to become stable, so they resist gaining electrons.
19. D – Ionization energy relates to removing electrons, not gaining them.
20. C – A highly negative electron affinity means the atom releases a lot of energy when it gains an electron
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