Periodic trends: atomic and ionic radii, ionization enthalpy, electron gain enthalpy, valence and oxidation states - One Line Questions

1. What is the oxidation state of an element in its elemental form (e.g., O2, Fe, S8)? — 0
2. The common oxidation states of elements in Group 1 are: — +1
3. The common oxidation states of elements in Group 2 are: — +2
4. The common oxidation states of elements in Group 17 are: — -1
5. In the compound SO2, what is the oxidation state of sulfur? — +4
6. In the compound KMnO4, what is the oxidation state of manganese (Mn)? — +7
7. For elements in Group 1 (alkali metals), the valence is typically: — 1
8. For elements in Group 18 (noble gases), the valence is typically: — 0
9. What is the oxidation state of sodium (Na) in NaCl? — +1
10. What is the oxidation state of chlorine (Cl) in NaCl? — -1
11. In the compound H2O, what is the oxidation state of oxygen? — -2
12. For elements in Group 17 (halogens), the valence is typically: — 1
13. Which of the following trends is correctly described? — Ionic radius of cations decreases as the positive charge increases.
14. How does electron gain enthalpy generally change across a period from left to right? — Becomes more negative (more energy released).
15. What is the general trend in electron gain enthalpy down a group? — Becomes less negative or more positive.
16. The element with the largest atomic radius in the second period is: — Lithium (Li)
17. What is the primary reason for the increase in ionization enthalpy across a period? — Increase in effective nuclear charge and decrease in atomic size.
18. What causes the ionic radius of an anion to be larger than its parent atom? — Decreased nuclear charge per electron.
19. Which of the following factors influences electron gain enthalpy? — Effective nuclear charge and electron configuration
20. A negative electron gain enthalpy indicates: — The atom readily accepts an electron.
21. Which of the following ions has the largest radius: F-, O2-, N3-? — N3-
22. Which element has the most negative electron gain enthalpy? — Chlorine (Cl)
23. The valence of elements in the same period: — Generally increases from left to right.
24. Which element has the highest first ionization enthalpy? — Helium (He)
25. What is the main factor responsible for the increase in atomic radius down a group? — Addition of new electron shells.
26. What is the main reason for the decrease in ionization enthalpy down a group? — Increase in atomic size and shielding effect.
27. What is the primary reason for the decrease in atomic radius across a period? — Increase in effective nuclear charge.
28. Why is the ionic radius of a cation smaller than its parent atom? — Increased nuclear charge per electron.
29. How does atomic radius generally change across a period from left to right in the periodic table? — Decreases
30. How does atomic radius generally change down a group in the periodic table? — Increases
31. How does ionization enthalpy generally change across a period from left to right? — Increases
32. How does ionization enthalpy generally change down a group? — Decreases
33. How does the ionic radius of a cation generally compare to its parent atom's atomic radius? — Smaller
34. How does the ionic radius of an anion generally compare to its parent atom's atomic radius? — Larger
35. Which element is expected to have the smallest atomic radius among Li, Be, B, C? — C
36. Which element has the lowest first ionization enthalpy? — Cesium (Cs)
37. Which element is expected to have the largest atomic radius among Na, K, Rb, Cs? — Cs
38. Which of the following ions has the smallest radius: Na+, Mg2+, Al3+? — Al3+
39. Which of the following factors influences atomic and ionic radii? — Effective nuclear charge and number of electron shells
40. Which of the following factors influences ionization enthalpy? — Effective nuclear charge, shielding effect, and atomic size
41. Which of the following elements has a positive electron gain enthalpy? — Nitrogen (N)
42. The element with the highest first ionization enthalpy in the third period is: — Argon (Ar)
43. Which of the following statements best describes atomic radius? — Half the distance between the nuclei of two identical atoms bonded together.
44. What is ionization enthalpy (or ionization energy)? — The energy required to remove the most loosely held electron from a neutral gaseous atom.
45. What is electron gain enthalpy? — The energy released when an electron is added to a neutral gaseous atom to form a gaseous anion.
46. The valence of an element is generally related to: — The number of electrons in the outermost shell.
47. Why does the second ionization enthalpy (IE2) of an element always exceed its first ionization enthalpy (IE1)? — The remaining electrons are more tightly held by the nucleus after one electron is removed.
48. What is meant by valence in chemistry? — The combining capacity of an element, usually determined by the number of electrons it can gain, lose, or share.
49. What is the oxidation state of an element? — The hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic.
50. The electron gain enthalpy of noble gases is generally positive because: — They have a stable, complete electron configuration.
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