Periodic trends: atomic and ionic radii, ionization enthalpy, electron gain enthalpy, valence and oxidation states - Question Bank

1. The element with the highest first ionization enthalpy in the third period is:
A) Sodium (Na)
B) Magnesium (Mg)
C) Chlorine (Cl)
D) Argon (Ar)
2. The element with the largest atomic radius in the second period is:
A) Carbon (C)
B) Nitrogen (N)
C) Oxygen (O)
D) Lithium (Li)
3. Which of the following trends is correctly described?
A) Atomic radius increases across a period.
B) Ionization enthalpy decreases down a group.
C) Electron gain enthalpy becomes more positive down a group.
D) Ionic radius of cations decreases as the positive charge increases.
4. The common oxidation states of elements in Group 17 are:
A) +1, -1
B) +2, -2
C) -1
D) +7
5. The common oxidation states of elements in Group 2 are:
A) +1
B) +2
C) -1
D) 0
6. The common oxidation states of elements in Group 1 are:
A) +1
B) +2
C) -1
D) 0
7. The valence of elements in the same period:
A) Generally increases from left to right.
B) Generally decreases from left to right.
C) Remains constant.
D) Varies randomly.
8. Which of the following factors influences electron gain enthalpy?
A) Effective nuclear charge and electron configuration
B) Number of neutrons
C) Atomic mass
D) Isotopic abundance
9. Which of the following factors influences ionization enthalpy?
A) Number of protons
B) Number of neutrons
C) Effective nuclear charge, shielding effect, and atomic size
D) Magnetic moment
10. Which of the following factors influences atomic and ionic radii?
A) Number of protons
B) Number of neutrons
C) Effective nuclear charge and number of electron shells
D) Electron spin
11. What is the oxidation state of an element in its elemental form (e.g., O2, Fe, S8)?
A) +1
B) -1
C) 0
D) Variable
12. In the compound KMnO4, what is the oxidation state of manganese (Mn)?
A) +2
B) +4
C) +7
D) -1
13. In the compound SO2, what is the oxidation state of sulfur?
A) +2
B) +4
C) -2
D) 0
14. In the compound H2O, what is the oxidation state of oxygen?
A) 0
B) +1
C) -1
D) -2
15. What is the oxidation state of chlorine (Cl) in NaCl?
A) 0
B) +1
C) -1
D) +7
16. What is the oxidation state of sodium (Na) in NaCl?
A) 0
B) +1
C) -1
D) +7
17. What is the oxidation state of an element?
A) The total number of electrons in an atom.
B) The number of electrons in the outermost shell.
C) The hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic.
D) The number of electrons an atom can gain, lose, or share.
18. The valence of an element is generally related to:
A) The number of protons in the nucleus.
B) The number of neutrons in the nucleus.
C) The number of electrons in the outermost shell.
D) The total number of electrons in the atom.
19. For elements in Group 18 (noble gases), the valence is typically:
A) 0
B) 1
C) 2
D) 8
20. For elements in Group 17 (halogens), the valence is typically:
A) 1
B) 2
C) 7
D) 8
21. For elements in Group 1 (alkali metals), the valence is typically:
A) 0
B) 1
C) 2
D) 7
22. What is meant by valence in chemistry?
A) The total number of electrons in an atom.
B) The number of electrons in the outermost shell of an atom.
C) The combining capacity of an element, usually determined by the number of electrons it can gain, lose, or share.
D) The charge of an ion formed by an element.
23. The electron gain enthalpy of noble gases is generally positive because:
A) They have very small atomic radii.
B) They have a stable, complete electron configuration.
C) Their nuclear charge is very high.
D) They have a strong tendency to lose electrons.
24. Which of the following elements has a positive electron gain enthalpy?
A) Oxygen (O)
B) Sulfur (S)
C) Nitrogen (N)
D) Bromine (Br)
25. Which element has the most negative electron gain enthalpy?
A) Fluorine (F)
B) Chlorine (Cl)
C) Bromine (Br)
D) Iodine (I)
26. What is the general trend in electron gain enthalpy down a group?
A) Becomes more negative.
B) Becomes less negative or more positive.
C) Remains constant.
D) Shows no specific trend.
27. How does electron gain enthalpy generally change across a period from left to right?
A) Becomes more negative (more energy released).
B) Becomes less negative or more positive (less energy released or energy absorbed).
C) Remains constant.
D) Shows no specific trend.
28. A negative electron gain enthalpy indicates:
A) Energy is absorbed when an electron is added.
B) The atom readily accepts an electron.
C) The resulting anion is unstable.
D) The atom has a strong tendency to lose electrons.
29. What is electron gain enthalpy?
A) The energy required to remove an electron from a gaseous anion.
B) The energy required to add an electron to a neutral gaseous atom.
C) The energy released when an electron is added to a neutral gaseous atom to form a gaseous anion.
D) The energy released when an atom gains an electron to form a gaseous cation.
30. Why does the second ionization enthalpy (IE2) of an element always exceed its first ionization enthalpy (IE1)?
A) The second electron is removed from a more stable configuration.
B) The remaining electrons are more tightly held by the nucleus after one electron is removed.
C) The nuclear charge increases after removing one electron.
D) The atomic radius increases after removing one electron.
31. Which element has the lowest first ionization enthalpy?
A) Lithium (Li)
B) Sodium (Na)
C) Potassium (K)
D) Cesium (Cs)
32. Which element has the highest first ionization enthalpy?
A) Helium (He)
B) Neon (Ne)
C) Argon (Ar)
D) Krypton (Kr)
33. What is the main reason for the decrease in ionization enthalpy down a group?
A) Increase in effective nuclear charge.
B) Increase in atomic size and shielding effect.
C) Decrease in nuclear charge.
D) Stronger attraction between nucleus and valence electrons.
34. How does ionization enthalpy generally change down a group?
A) Increases
B) Decreases
C) Remains constant
D) Increases initially, then decreases
35. What is the primary reason for the increase in ionization enthalpy across a period?
A) Decrease in effective nuclear charge.
B) Increase in shielding effect.
C) Increase in effective nuclear charge and decrease in atomic size.
D) Addition of electron shells.
36. How does ionization enthalpy generally change across a period from left to right?
A) Increases
B) Decreases
C) Remains constant
D) Initially decreases, then increases
37. What is ionization enthalpy (or ionization energy)?
A) The energy released when an electron is added to a neutral atom.
B) The energy required to remove the most loosely held electron from a neutral gaseous atom.
C) The energy required to remove an electron from a gaseous cation.
D) The energy released when an atom gains an electron to form a gaseous anion.
38. Which of the following ions has the largest radius: F-, O2-, N3-?
A) F-
B) O2-
C) N3-
D) They have the same radius.
39. Which of the following ions has the smallest radius: Na+, Mg2+, Al3+?
A) Na+
B) Mg2+
C) Al3+
D) They have the same radius.
40. What causes the ionic radius of an anion to be larger than its parent atom?
A) Decreased nuclear charge per electron.
B) Removal of electrons.
C) Increased nuclear attraction.
D) Fewer electron shells.
41. How does the ionic radius of an anion generally compare to its parent atom's atomic radius?
A) Larger
B) Smaller
C) Equal
D) Varies unpredictably
42. Why is the ionic radius of a cation smaller than its parent atom?
A) Increased electron-electron repulsion.
B) Increased nuclear charge per electron.
C) Decreased number of protons.
D) Addition of electrons.
43. How does the ionic radius of a cation generally compare to its parent atom's atomic radius?
A) Larger
B) Smaller
C) Equal
D) Varies unpredictably
44. Which element is expected to have the smallest atomic radius among Li, Be, B, C?
A) Li
B) Be
C) B
D) C
45. Which element is expected to have the largest atomic radius among Na, K, Rb, Cs?
A) Na
B) K
C) Rb
D) Cs
46. What is the main factor responsible for the increase in atomic radius down a group?
A) Increase in effective nuclear charge.
B) Addition of new electron shells.
C) Decrease in nuclear charge.
D) Stronger attraction between nucleus and valence electrons.
47. How does atomic radius generally change down a group in the periodic table?
A) Increases
B) Decreases
C) Remains constant
D) Increases initially, then decreases
48. What is the primary reason for the decrease in atomic radius across a period?
A) Increase in the number of electron shells.
B) Decrease in nuclear charge.
C) Increase in effective nuclear charge.
D) Repulsion between electrons in the same shell.
49. How does atomic radius generally change across a period from left to right in the periodic table?
A) Increases
B) Decreases
C) Remains constant
D) Increases initially, then decreases
50. Which of the following statements best describes atomic radius?
A) The distance from the nucleus to the outermost electron shell.
B) The distance from the nucleus to the outermost electron in a neutral atom.
C) Half the distance between the nuclei of two identical atoms bonded together.
D) The distance from the nucleus to the valence shell in an ion.
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