Rucete ✏ AP Chemistry In a Nutshell
2. The Periodic Table — Practice Questions 2
This set explores periodic trends and relationships in new ways, with questions focused on electron affinity, atomic structure, PES interpretation, diagonal relationships, and ion behavior. All items are freshly designed to avoid repetition from earlier sets and reinforce deep conceptual understanding.
(Multiple Choice — Click to Reveal Answer)
1. Which group contains elements with full outer s and p orbitals?
(A) Alkali metals
(B) Alkaline earth metals
(C) Halogens
(D) Noble gases
Answer
(D) — Noble gases have full s and p sublevels, making them stable and unreactive.
2. Which element is a metalloid?
(A) Barium
(B) Arsenic
(C) Fluorine
(D) Krypton
Answer
(B) — Arsenic lies along the “stair-step” line and exhibits both metallic and nonmetallic properties.
3. What property generally increases from bottom to top within a group?
(A) Atomic radius
(B) Metallic character
(C) Ionization energy
(D) Reactivity
Answer
(C) — Ionization energy increases from bottom to top due to reduced shielding and stronger nuclear attraction.
4. Which of the following best explains why cations are smaller than their parent atoms?
(A) More energy levels
(B) Increased shielding
(C) Loss of outer electrons
(D) Greater repulsion among electrons
Answer
(C) — Cations lose electrons, often from the outermost shell, reducing size and increasing effective nuclear pull.
5. What does a higher peak in a PES spectrum indicate?
(A) Higher ionization energy
(B) More electrons in that orbital
(C) Smaller nucleus
(D) Lower shielding
Answer
(B) — Peak intensity in PES reflects the number of electrons in that orbital/subshell.
6. Which of the following is NOT a physical property that varies across the periodic table?
(A) Density
(B) Boiling point
(C) Ionization energy
(D) Atomic number
Answer
(D) — Atomic number is sequential and does not vary in a trend like physical properties.
7. What element has the highest first ionization energy?
(A) Cesium
(B) Oxygen
(C) Fluorine
(D) Helium
Answer
(D) — Helium has the highest ionization energy due to small size and full shell.
8. Which group contains elements that readily lose one electron to form +1 ions?
(A) Group 1 (alkali metals)
(B) Group 2 (alkaline earth metals)
(C) Group 17 (halogens)
(D) Group 18 (noble gases)
Answer
(A) — Alkali metals have one valence electron and easily form +1 cations.
9. Which element is expected to have the largest atomic radius?
(A) Li
(B) Na
(C) K
(D) Cs
Answer
(D) — Atomic radius increases down a group; Cs is at the bottom of Group 1.
10. Which of the following elements has the most metallic character?
(A) F
(B) O
(C) Cs
(D) Cl
Answer
(C) — Metallic character increases down and to the left; Cs is the most metallic listed.
11. What term describes the average mass of an element's naturally occurring isotopes?
(A) Mass number
(B) Atomic number
(C) Atomic mass
(D) Isotopic mass
Answer
(C) — Atomic mass is the weighted average of all naturally occurring isotopes.
12. Which of the following ions is smallest in size?
(A) Mg²⁺
(B) Na⁺
(C) Al³⁺
(D) K⁺
Answer
(C) — Al³⁺ has the greatest charge-to-electron ratio, pulling electrons closer and reducing size.
13. Which property increases across a period and decreases down a group?
(A) Atomic radius
(B) Electron affinity
(C) Ionization energy
(D) Both B and C
Answer
(D) — Both ionization energy and electron affinity increase across a period and decrease down a group.
14. What is the general trend in electronegativity from left to right across a period?
(A) Decreases
(B) Increases
(C) Remains the same
(D) First increases then decreases
Answer
(B) — Electronegativity increases across a period as atoms more strongly attract electrons.
15. Which of the following has the same electron configuration as neon?
(A) Na⁺
(B) Mg⁺
(C) F⁻
(D) Both A and C
Answer
(D) — Both Na⁺ and F⁻ have 10 electrons, same as Ne: 1s² 2s² 2p⁶.
16. Which orbital type is filled in the transition metals?
(A) s
(B) p
(C) d
(D) f
Answer
(C) — Transition metals fill the d sublevel.
17. What element is likely to form a –2 ion?
(A) O
(B) N
(C) Na
(D) Mg
Answer
(A) — Oxygen typically gains 2 electrons to form O²⁻.
18. Which of these elements is least likely to form an ion?
(A) He
(B) Na
(C) Br
(D) Ca
Answer
(A) — Helium is a noble gas and chemically inert; it rarely forms ions.
19. The periodic table is arranged by increasing:
(A) Atomic mass
(B) Ionization energy
(C) Atomic number
(D) Number of isotopes
Answer
(C) — The modern periodic table is organized by increasing atomic number.
20. What type of ion is larger than its parent atom?
(A) Cation
(B) Anion
(C) Isotope
(D) Neutral atom
Answer
(B) — Anions gain electrons, increasing repulsion and electron cloud size.
21. Which best defines effective nuclear charge (Zeff)?
(A) Total number of protons
(B) Attraction between nucleus and core electrons
(C) Net positive charge felt by valence electrons
(D) Difference between atomic mass and atomic number
Answer
(C) — Zeff is the net nuclear attraction experienced by valence electrons, reduced by shielding.
22. Which property is NOT periodic?
(A) Boiling point
(B) Atomic number
(C) Electron configuration
(D) Effective nuclear charge
Answer
(B) — Atomic number increases steadily and is not a periodic property.
23. What is the most reactive group of nonmetals?
(A) Noble gases
(B) Halogens
(C) Transition metals
(D) Metalloids
Answer
(B) — Halogens are very reactive, especially with metals, due to their high electronegativity.
24. Which property determines whether an element is a metal or nonmetal?
(A) Ionization energy
(B) Electronegativity
(C) Electron configuration
(D) All of the above
Answer
(D) — All three properties influence metallic vs. nonmetallic behavior.
25. Which element is expected to have a low electron affinity?
(A) Cl
(B) F
(C) Ne
(D) O
Answer
(C) — Noble gases like Ne have full shells and resist gaining electrons (positive or near-zero electron affinity).
26. Which element has the largest second ionization energy?
(A) Na
(B) Mg
(C) Al
(D) K
Answer
(A) — After Na⁺ loses its one valence electron, removing a second electron requires breaking into a full inner shell (very high energy).
27. Which element would most likely exhibit an anomalous electron configuration?
(A) Sc
(B) Mn
(C) Cu
(D) Zn
Answer
(C) — Cu prefers a half-filled 4s¹ 3d¹⁰ configuration for added stability.
28. Which of the following best explains why atomic radius decreases across a period?
(A) Electron shielding increases
(B) More energy levels are added
(C) Nuclear charge increases without much added shielding
(D) Proton number stays the same
Answer
(C) — More protons increase nuclear pull while shielding remains mostly constant across a period.
29. Which element has the lowest electronegativity?
(A) Cs
(B) Li
(C) Mg
(D) Sr
Answer
(A) — Cs is farthest down and left; it's the least electronegative element among those listed.
30. The element with the electron configuration [Kr] 5s² 4d⁵ is:
(A) Nb
(B) Mo
(C) Tc
(D) Ru
Answer
(B) — Molybdenum exhibits this configuration due to d-subshell stability.
31. Which factor has the greatest effect on shielding in atoms of the same period?
(A) Proton number
(B) Number of valence electrons
(C) Number of inner-shell electrons
(D) Atomic mass
Answer
(C) — Shielding depends on inner-shell electrons repelling outer electrons.
32. Which of the following atoms is most likely to form a +3 ion?
(A) Na
(B) Al
(C) S
(D) Cl
Answer
(B) — Aluminum commonly loses three electrons to form Al³⁺.
33. Which element would require the greatest energy to form a +2 ion?
(A) Sr
(B) Ca
(C) Be
(D) Mg
Answer
(C) — Be is small with high Zeff, so removing 2 electrons requires more energy.
34. Which group has elements with both low ionization energy and low electron affinity?
(A) Group 1 (alkali metals)
(B) Group 2 (alkaline earth metals)
(C) Group 17 (halogens)
(D) Group 18 (noble gases)
Answer
(B) — Alkaline earth metals don’t attract electrons strongly and lose them fairly easily.
35. Which of the following atoms has the greatest number of core electrons?
(A) Cl
(B) Br
(C) I
(D) At
Answer
(D) — Astatine is lower in the group and has the most inner (core) electrons.
36. Explain why the atomic radius of an anion is larger than that of its neutral atom.
Answer
Anions gain electrons, increasing electron–electron repulsion and causing the electron cloud to expand, which increases atomic radius.
37. Why is the second ionization energy of sodium much higher than the first?
Answer
Removing the second electron would disrupt a full noble gas configuration, requiring much more energy.
38. Describe the diagonal relationship between lithium and magnesium.
Answer
Li and Mg, though in different groups, have similar properties such as solubility trends and oxide/hydroxide behavior due to similar charge density and ionic size.
39. What trend in effective nuclear charge (Zeff) explains the decrease in atomic radius across a period?
Answer
Zeff increases across a period due to increasing proton number without added shielding, pulling electrons closer and reducing atomic radius.
40. Why do halogens have high electron affinities?
Answer
Halogens are one electron away from a full octet, so they strongly attract additional electrons, releasing significant energy upon gaining one.
41. Define shielding and describe how it affects ionization energy.
Answer
Shielding is the blocking of nuclear attraction by inner electrons. It reduces the energy needed to remove valence electrons, lowering ionization energy.
42. Why is Francium predicted to have the lowest electronegativity?
Answer
Francium has a large atomic radius and strong shielding, so its nucleus exerts little pull on bonding electrons.
43. Identify an element with a filled 4f sublevel and describe its placement on the periodic table.
Answer
Ytterbium (Yb) has a filled 4f sublevel and is located in the lanthanide series (f-block).
44. What does a steep drop in ionization energy on a graph of successive ionizations suggest?
Answer
It indicates removal of a core electron after all valence electrons have been removed, requiring much higher energy.
45. How does atomic structure explain why group 1 metals are highly reactive?
Answer
They have a single valence electron that is loosely held due to large atomic radius and low ionization energy, making it easy to lose in reactions.
46. Why do noble gases have negligible electron affinity values?
Answer
Their valence shells are full, so they don’t tend to gain electrons, and little energy is released if they do.
47. What is meant by “periodicity” in the periodic table?
Answer
Periodicity refers to the recurring trends in physical and chemical properties across periods due to regular changes in electron configurations.
48. Explain the placement of hydrogen on the periodic table in terms of its dual properties.
Answer
Hydrogen is in Group 1 due to having 1 electron, but it also resembles halogens in that it needs one electron to fill its shell, showing dual behavior.
49. What type of ion does sulfur typically form and why?
Answer
Sulfur forms S²⁻ ions by gaining two electrons to complete its valence shell and achieve a stable octet.
50. Describe a trend in metallic character across a period and down a group.
Answer
Metallic character decreases across a period (left to right) and increases down a group due to easier loss of valence electrons.