CORRECT ANSWERS WITH RATIONALES
GRADED A+ LATEST
1. Which of the following elements has the smallest atomic radius?
A) Li
B) Be
C) B
D) C
E) F
Answer: E
Rationale: Atomic radius decreases across a period due to increasing nuclear
charge; fluorine is the smallest.
2. Which quantum number describes the orientation of an orbital?
A) Principal (n)
B) Angular momentum (l)
C) Magnetic (m_l)
D) Spin (m_s)
E) None of the above
Answer: C
Rationale: The magnetic quantum number (m_l) indicates orbital orientation in
space.
3. Which of the following ions is isoelectronic with neon (Ne)?
A) F⁻
B) O²⁻
C) Na⁺
D) All of the above
E) None of the above
Answer: D
Rationale: F⁻, O²⁻, and Na⁺ all have 10 electrons, same as neon.
,4. Which element has the highest electronegativity?
A) Li
B) C
C) O
D) F
E) Ne
Answer: D
Rationale: Fluorine is the most electronegative element.
5. Which type of bond involves the sharing of electrons between atoms?
A) Ionic
B) Covalent
C) Metallic
D) Hydrogen
E) Van der Waals
Answer: B
Rationale: Covalent bonds result from electron sharing.
6. Which of the following compounds exhibits polar covalent bonding?
A) NaCl
B) H₂O
C) Cl₂
D) Ne
E) MgO
Answer: B
Rationale: Water has a polar covalent bond due to difference in electronegativity
and molecular geometry.
7. Which of the following is a property of ionic compounds?
A) Low melting point
B) Conduct electricity as solids
C) Brittle and crystalline
D) Soft and malleable
E) Nonpolar
Answer: C
,Rationale: Ionic compounds are hard, brittle, and form crystalline solids; they
conduct electricity when molten or dissolved.
8. What is the electron configuration of O²⁻?
A) 1s² 2s² 2p⁴
B) 1s² 2s² 2p⁶
C) 1s² 2s² 2p³
D) 1s² 2s² 2p⁵
E) 1s² 2s² 2p²
Answer: B
Rationale: O²⁻ gains two electrons to achieve a full 2p shell like neon.
9. Which of the following molecules has a trigonal planar geometry?
A) CH₄
B) CO₂
C) BF₃
D) NH₃
E) H₂O
Answer: C
Rationale: BF₃ has three bonding pairs and no lone pairs on the central atom,
forming trigonal planar geometry.
10. Which type of hybridization occurs in CH₄?
A) sp
B) sp²
C) sp³
D) dsp²
E) d²sp³
Answer: C
Rationale: Carbon in CH₄ forms four sigma bonds and undergoes sp³
hybridization.
, 11. Which of the following best explains why F₂ has a lower bond energy than O₂?
A) F₂ is diatomic
B) F₂ has lone pair-lone pair repulsion
C) F₂ is polar
D) F₂ is ionic
E) O₂ has weaker bonds
Answer: B
Rationale: F₂ bond is weakened due to repulsion between lone pairs on the
fluorine atoms.
12. Which element has the lowest first ionization energy?
A) Li
B) Na
C) K
D) Rb
E) Cs
Answer: E
Rationale: Ionization energy decreases down a group; cesium requires the least
energy to remove an electron.
13. Which molecule is nonpolar despite containing polar bonds?
A) H₂O
B) CO₂
C) NH₃
D) HF
E) HCl
Answer: B
Rationale: CO₂ is linear; bond dipoles cancel, making the molecule nonpolar.
14. Which of the following ions forms an ionic compound with Cl⁻?
A) Na⁺
B) Mg²⁺
C) Al³⁺
D) All of the above
E) None of the above
Answer: D