Trends in atomic and ionic radii, ionization potential and electron affinity - One Line Questions

1. Which of the following isoelectronic species will have the smallest ionic radius? — Ca2+
2. Which of the following trends is INCORRECT? — Ionization potential decreases across a period.
3. Which of the following elements has a positive electron affinity (meaning energy is required to add an electron)? — Noble Gases (e.g., Ne)
4. Which ion is smaller: Cl- or F-? — F-
5. The trend in atomic radii down Group 17 (Halogens) is: — I > Br > Cl > F
6. Why does Fluorine have a lower electron affinity than Chlorine? — The small size of the Fluorine atom leads to significant electron-electron repulsion when an electron is added.
7. The energy required to remove the first electron from a neutral atom is the first ionization energy. The energy required to remove the second electron from the resulting unipositive ion is the second ionization energy. Which relationship is ALWAYS true? — IE1(X) < IE2(X)
8. Why does ionization potential generally increase across a period? — Increase in effective nuclear charge and decrease in atomic radius
9. Electron affinity generally increases across a period. Why? — Increase in effective nuclear charge and decrease in atomic radius, leading to stronger attraction for an incoming electron
10. Which factor contributes most to the decrease in ionization potential down a group? — Increase in the distance of the valence electron from the nucleus and increased shielding
11. Why does electron affinity generally decrease down a group? — Increase in atomic radius and shielding, reducing the attraction for the incoming electron
12. What is the primary reason for the decrease in atomic radius across a period? — Increase in effective nuclear charge with electrons added to the same shell
13. Why does an anion have a larger ionic radius than its parent atom? — Increased electron-electron repulsion and decreased effective nuclear charge per electron
14. Why does a cation have a smaller ionic radius than its parent atom? — Decreased effective nuclear charge per electron and reduced electron-electron repulsion
15. As one moves down a group, electron affinity generally: — Decreases
16. The effective nuclear charge experienced by an outer electron generally increases as one moves across a period from left to right. What effect does this have on atomic radius? — It causes the atomic radius to decrease.
17. As one moves down a group in the periodic table, what generally happens to the ionization potential? — It decreases
18. As one moves down a group in the periodic table, what generally happens to the atomic radius? — It increases
19. When an atom loses an electron to form a cation, its ionic radius is generally: — Smaller than its atomic radius
20. When an atom gains an electron to form an anion, its ionic radius is generally: — Larger than its atomic radius
21. Which of the following is the correct order of increasing electron affinity for Li, Be, B, C? — Be < B < C < Li
22. Which of the following is the correct order of increasing atomic radii for Li, Be, B, C? — C < B < Be < Li
23. Which of the following is the correct order of decreasing first ionization potential for Li, Be, B, C? — C > B > Be > Li
24. Which of the following is the correct order of decreasing atomic radii for Li, Be, B, C? — Li > Be > B > C
25. Which of the following pairs of elements would have the largest difference in atomic radii? — Na and K
26. Which element in the second period has the highest first ionization potential? — Neon (Ne)
27. Which element in the second period has the highest (most negative) electron affinity? — Fluorine (F)
28. Which element in the second period has the smallest atomic radius? — Neon (Ne)
29. Which of the following ions has the largest radius? — F-
30. Which of the following has the highest first ionization potential? — Mg
31. Which of the following has the highest (most negative) electron affinity? — Si
32. Which ion is larger: Na+ or K+? — K+
33. Which of the following elements has an unusually low first ionization potential compared to its neighbors in the same period? — Oxygen (O)
34. Which of the following factors primarily determines the atomic radius of an element? — Number of electron shells and effective nuclear charge
35. In the series O2-, F-, Na+, Mg2+, which species has the largest radius? — O2-
36. In the series O2-, F-, Na+, Mg2+, which species has the smallest radius? — Mg2+
37. Why does Oxygen have a lower first ionization energy than Nitrogen? — The electron removed from Oxygen is from a doubly occupied p-orbital, leading to repulsion.
38. Which statement best explains the anomalous electron affinity of some elements like Phosphorus (P) compared to Sulfur (S)? — The added electron in Phosphorus enters a half-filled p-orbital, experiencing less repulsion than in Sulfur's doubly occupied p-orbital.
39. For most elements, the addition of an electron results in energy release, meaning electron affinity is typically: — Negative
40. Which of the following is expected to have the largest atomic radius? — Potassium (K)
41. Which of the following ions has the smallest radius? — Ca2+
42. Which element is expected to have the highest second ionization energy? — Sodium (Na)
43. Why is the atomic radius of Sodium (Na) larger than that of Magnesium (Mg)? — Magnesium has a higher effective nuclear charge acting on its valence electrons.
44. What is ionization potential (or ionization energy)? — The energy required to remove the most loosely held electron from an isolated gaseous atom.
45. What is electron affinity? — The energy change that occurs when an electron is added to a neutral gaseous atom to form a negative ion.
46. Consider isoelectronic species (same number of electrons). For example, O2-, F-, Na+, Mg2+. Which statement is true about their radii? — The radius decreases with increasing nuclear charge.
47. The second ionization potential of an element is always higher than its first ionization potential. Why? — The second electron is removed from a positively charged ion, requiring more energy.
48. Why does Sodium (Na) have a very high second ionization energy? — The second electron is removed from a noble gas configuration.
49. Why do noble gases have positive electron affinities? — They have a stable, filled valence electron shell, and adding an electron requires forcing it into a higher energy level or causing repulsion.
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