Physical Chemistry Questions and Answers – Electronic Structure of Polyatomic Atoms: Valence Bond Method

This set of Physical Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Electronic Structure of Polyatomic Atoms: Valence Bond Method”.

1. What are polyatomic ions?
a) Ions which consist of one atom only
b) Ions which consist of no atoms
c) Ions which are not stable
d) Ions which consist of more than one atom
View Answer

Answer: d
Explanation: The ions that contain more than one atom are called polyatomic ions. Here, poly stands for many. For example, chromate ion contains one chromium and two oxygen atoms. The atoms in such ions are usually bonded to each other by covalent bonds and stay together as a charged unit.

2. What are the constituent ions in the ionic compound Ca(MnO4)2?
a) One ion of MnO4
b) Two ions of MnO4
c) Four ions of MnO4
d) No ions of MnO4
View Answer

Answer: b
Explanation: When analyzing the formula of an ionic compound Ca(MnO4)2, MnO4 permanganate is one of the polyatomic ions that is found in the given compound. Because the net charge of the compound must be zero, the ionic compound Ca(MnO4)2 contains one Ca2+ cation and two MnO4 anions.

3. In which year the valence bond theory was introduced?
a) 1928
b) 1920
c) 1930
d) 1935
View Answer

Answer: a
Explanation: In 1928, Linus Pauling combined Lewis’s pair bonding idea with the Heitler-London theory to propose valence bond theory. Valence bond theory was developed to describe resonance and orbital hybridization.

4. Which of the following has the bond angle of 120 degrees?
a) PH3
b) NCl3
c) BCl3
d) ClF3
View Answer

Answer: c
Explanation: The hybridization of BCl3 is sp2 which means BCl3 has one s-orbital and two p-orbitals of the same shell of an atom that mix to form three new equivalent orbitals. And the geometry of BCl3 is trigonal planar, this is because it has the bond angle of 120 degrees.

5. What is the hybridization of XeF4?
a) sp3d2
b) sp3
c) sp2d2
d) sp3d
View Answer

Answer: a
Explanation: When XeF4 forms two 5p orbital electrons which are in the excited state move to the vacant 5d orbitals to fill them. This results in 4 unpaired electrons which includes 2 in 5p and 2 in 5d orbitals respectively. This it has sp3d2 hybridization.

6. Which of the following has the sp2 hybridization?
a) C2H2
b) C2H4
c) BeCl2
d) C2H6
View Answer

Answer: b
Explanation: The Lewis structure of ethane (C2H4) makes the carbon atoms sp2 hybridized. The sp2 hybridization involves 2 carbon atoms combines with 4 atoms of hydrogen. In ethane molecule, there is 5 sigma and 1 pi bond. The angle of sp2 hybridized ethane is 120 degrees.

7. What is the hybridization in [Ni (CN)4]2-?
a) sp3
b) d2sp2
c) dsp2
d) d2sp3
View Answer

Answer: c
Explanation: [Ni (CN)4]2- has a square planar geometry which is formed by dsp2 hybridization. In the formation of compound [Ni (CN)4]2-, two unpaired d-electrons get paired up making one of the 3d orbitals empty. And since, there are no unpaired electrons available therefore, this complex compound is diamagnetic in nature.

8. Which of the following is relevant structure and hybridization for [Mn(CN)6]3-?
a) dsp2 and octahedral
b) d2sp3 and octahedral
c) sp3d2 and trigonal
d) sp3d2 and square planar
View Answer

Answer: b
Explanation: In the complex [Mn(CN)6]3-, the Mn3+ ion has d4 outer electronic configuration. It is an inner orbital complex, thus inner d-orbitals are used which results in d2sp3 hybridization. And, the molecular geometry of the given complex is octahedral.

9. Which of the following statements are true about valence bond theory?
Statement 1: There should be greater overlapping between atomic orbitals.
Statement 2: There must be close proximity between two atoms and pairing of electrons must have opposite signs.
a) Statement 1 is true but statement 2 is false
b) Statement 2 is true but statement 1 is false
c) Statement 1 and statement 2, both are true
d) Statement 1 and statement 2, both are false
View Answer

Answer: c
Explanation: In valence bond theory, orbitals that overlap extensively from bonds that are stronger than those that have less overlap. The close proximity between the atoms and pairing of electrons that have opposite signs makes the bonds much stronger and stable.

10. What is the geometry of XeF4?
a) Square planar
b) Octahedral
c) Triangular planar
d) Trigonal bipyramidal
View Answer

Answer: a
Explanation: XeF4 consists of two lone pair electrons. So, according to the VSEPR theory, the net electronic repulsions have to be least in order to acquire a stable state. In order to achieve this, the lone pairs lie in a perpendicular plane in an octahedral arrangement opposite (180°) from each other. Therefore, XeF4 molecular geometry is square planar.

11. Which of the following have sp3 hybridization?
a) BF3, NH3
b) SF4, BeH2
c) H2S, BF3
d) NH3, H2O
View Answer

Answer: d
Explanation: In the ammonia molecule (NH3), 2s and 2p orbitals create four sp3 hybrid orbitals, one of which is occupied by a lone pair of electrons. In a water molecule, two sp3 hybrid orbitals are occupied by the two lone pairs of the oxygen atom, while the other two bond with hydrogen. Thus, NH3 and H2O have sp3 hybridization.

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