Periodic Trends Quiz
Questions: 16 · 10 minutes
1. Which element has the largest atomic radius among lithium, sodium, and potassium?
Lithium, because its valence electron occupies the lowest principal energy level.
Sodium, because it has the best balance between nuclear charge and shielding.
Potassium, because each step down the group adds an occupied principal shell.
They are approximately equal because each has one valence electron.
2. An element shows a very large jump between its third and fourth successive ionization energies. What does this most strongly suggest?
The element normally gains three electrons to complete its valence shell.
The element has three valence electrons, and the fourth electron would come from a core shell.
The element has four valence electrons with nearly identical removal energies.
The element is a noble gas with three occupied principal energy levels.
3. Which is the smallest species among N3−, O2−, F−, and Na+?
N3−, because its large negative charge compresses its electron cloud.
Na+, because it has the greatest number of protons attracting the same number of electrons.
F−, because fluorine’s high electronegativity always produces the smallest ion.
O2−, because oxygen has fewer occupied electron shells than sodium.
4. O2−, F−, Na+, and Mg2+ each have 10 electrons. Which species has the largest radius?
O2−, because it has the fewest protons attracting the same number of electrons.
Mg2+, because its positive charge pushes the electrons outward.
F−, because fluorine is the most electronegative element in the set.
Na+, because sodium has the largest neutral atomic radius in the set.
5. From sodium to chlorine across Period 3, atomic radius generally decreases. Which change most directly accounts for this pattern?
Core shielding changes relatively little while increasing nuclear charge strengthens attraction to the valence shell.
The number of occupied principal shells steadily decreases across the period.
Core shielding increases more rapidly than nuclear charge.
Valence electrons move progressively farther from the nucleus as orbitals are filled.
6. Rubidium generally reacts more vigorously with water than sodium. What is the best explanation?
Rubidium is more electronegative, so it attracts oxygen from water more strongly.
Rubidium has a smaller radius, placing its valence electron closer to the nucleus.
Rubidium has fewer occupied electron shells, reducing electron-electron repulsion.
Rubidium’s outer electron is more shielded and is removed more easily.
7. How does the radius of a potassium atom compare with the radius of a K+ ion?
They are the same size because both have the same number of protons.
The ion is larger because its remaining electrons experience less attraction to the nucleus.
The atom is larger because forming K+ removes its outer electron shell.
The ion is larger because losing an electron increases shielding.
8. Which element has the strongest metallic character among silicon, phosphorus, germanium, and arsenic?
Silicon, because metallic character increases toward the upper right of the table.
Phosphorus, because nonmetals readily lose electrons to form cations.
Germanium, because metallic character generally increases down a group and toward the left.
Arsenic, because moving right across a period increases metallic character.
9. Magnesium has a slightly higher first ionization energy than aluminum. What best explains this exception to the general across-period trend?
Aluminum’s first removed electron is in a higher-energy 3p orbital, while magnesium’s is removed from 3s.
Magnesium has more inner shells, so its valence electrons experience greater shielding.
Aluminum has a completely filled valence shell that strongly repels an added electron.
Aluminum has fewer protons available to attract its valence electrons.
10. Which element has the highest electronegativity among carbon, nitrogen, oxygen, and fluorine?
Nitrogen
Oxygen
Fluorine
Carbon
11. Which statement correctly describes the acid–base trend of common oxides across Period 3?
Na2O is acidic, while SiO2 is basic.
MgO is amphoteric, while Al2O3 is strongly basic only.
Al2O3 is acidic only, while phosphorus oxides are basic.
Na2O is basic, while Al2O3 is amphoteric.
12. Which bond is expected to have the greatest electronegativity difference?
H–F
N–H
O–H
C–H
13. Why does atomic radius generally decrease from left to right across a period?
The number of protons decreases while the number of valence electrons increases.
Additional electron shells are added, bringing the valence electrons closer to the nucleus.
Core-electron shielding rises enough to cancel the increase in nuclear charge.
Nuclear charge increases while electrons enter the same principal shell, strengthening attraction to the nucleus.
14. Chlorine generally reacts more readily than bromine as a halogen. Which explanation best applies the group trend?
Chlorine has more occupied shells, allowing it to accept electrons more easily.
Bromine holds its valence electrons more tightly because atomic radius increases down the group.
Bromine has fewer core electrons, so its valence shell is less shielded.
Chlorine’s smaller radius allows its nucleus to attract an incoming electron more strongly.
15. Why does first ionization energy generally decrease down a group?
Atoms have fewer occupied energy levels, so valence electrons experience greater repulsion.
Valence electrons are farther from the nucleus and more shielded by inner electrons.
Nuclear charge decreases because elements lower in a group contain fewer protons.
Valence electrons move into the same shell but occupy lower-energy orbitals.
16. Sodium and magnesium are in the same period. Which comparison of their atomic radii is correct?
Magnesium is larger because it has one more occupied electron shell.
Sodium is larger because magnesium’s greater nuclear charge pulls same-shell electrons closer.
Magnesium is larger because its greater nuclear charge increases electron-electron repulsion.
They are approximately equal because their valence electrons occupy the same shell.