Aim to answer every question before checking. Missed questions point you to the sections you need most.
1. (2.1) The modern periodic table is arranged by:
B. Moseley's X-ray work (1913) showed atomic number, not mass, is the ordering principle. Mendeleev's original mass-ordered table had to be rearranged in places (e.g., Te vs. I).
2. (2.1) Elements in the same column (group) share:
A. Group 1 elements all have one s electron; halogens all have seven valence electrons. Identical valence patterns produce similar chemistry.
3. (2.2) Metalloids (semi-metals):
C. Metalloids sit along the staircase line. Semiconductor properties (like silicon's) come from this intermediate character.
4. (2.2) Metals are characterized by:
D. Delocalized "electron sea" bonding accounts for all of these properties. Nonmetals generally do the opposite.
5. (2.3) Alkali metals (Group 1) feature:
B. Group 1 metals have the lowest first ionization energies: they eagerly lose that one electron to reach the previous noble-gas configuration.
6. (2.3) Noble gases (Group 18):
A. With ns² np⁶ (except He: 1s²), they resist gaining or losing electrons. Heavier ones (Xe, Kr) can form compounds with very electronegative partners.
7. (2.4) Transition metals:
C. Variable oxidation states (Fe²⁺/Fe³⁺, Mn in many states) and colored compounds are hallmarks of d-block chemistry.
8. (2.4) Coordination complexes of transition metals:
D. Crystal-field theory predicts that ligand fields split d orbitals. Electronic transitions in this split set absorb visible light, so solutions of Cu²⁺, Cr³⁺, etc. look colored.
9. (2.5) Atomic radius generally:
B. Zeff rises across a period, pulling electrons closer. Down a group, a new shell is added each time, outweighing the charge increase.
10. (2.5) Atomic radius increases down a group because:
A. Each period lies in a higher-n shell. Cs is far larger than Li because it has five more shells of electrons.
11. (2.6) A cation is:
C. Losing electrons can even remove a whole shell (e.g., Na → Na⁺), dramatically shrinking the species.
12. (2.6) An anion is:
D. Adding electrons raises mutual repulsion and effectively lowers Zeff per electron, so the cloud expands.
13. (2.7) Ionization energy generally:
B. Higher Zeff and smaller radius across a period → electrons held tighter. Larger shells down a group → electrons easier to remove.
14. (2.7) The first ionization energy is:
A. Always endothermic. Successive ionizations (second, third) grow larger; huge jumps occur after removing all valence electrons.
15. (2.8) Electron affinity is:
C. Halogens have the most negative (most exothermic) electron affinities. Noble gases have near-zero or slightly positive values.
16. (2.8) Halogens have:
D. Cl⁻ is the classic example. Gaining a single electron gives [Ar] and releases significant energy.
17. (2.9) Electronegativity is best described as:
B. Pauling values run from about 0.7 (Cs) to 4.0 (F). Differences in EN predict bond polarity and ionic character.
18. (2.9) The most electronegative element is:
A. FONCl mnemonic (descending order): F > O > N > Cl. Francium (lower left) is least electronegative.
19. (2.10) Metallic character generally:
C. Metals are electropositive (low IE, low EN). These properties strengthen down-left, so Cs and Fr are the "most metallic."
20. (2.10) Metallic character is highest in:
D. The lower left has the lowest ionization energies. These elements readily give up electrons to form cations.
21. (2.11) Effective nuclear charge (Zeff) experienced by an outer electron is:
B. Slater's rules let you estimate Zeff. Inner electrons partially screen the nucleus, so outer electrons feel less than the full Z.
22. (2.11) Zeff and atomic radius are related because:
A. Across a period, Zeff grows while n stays constant. The extra pull contracts the valence shell, explaining the trend.
23. (2.12) The observed configurations of Cr and Cu depart from Aufbau prediction because:
C. Cr is [Ar] 4s¹ 3d⁵; Cu is [Ar] 4s¹ 3d¹⁰. Extra exchange stabilization of half- and fully-filled subshells beats Aufbau here.
24. (2.12) The lanthanide contraction refers to:
D. 4f electrons shield the nucleus poorly, so Zeff rises sharply across the lanthanides. Elements just after Yb (Hf, Ta, W) end up similar in size to their 4d counterparts (Zr, Nb, Mo).
