Chem-4: Chemical Bonding and Molecular Structure30 Questions
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1. The force that holds atoms together in a molecule or compound is called a:
A. Chemical bond
B. Van der Waals force only
C. Nuclear force
D. Frictional force
Answer: A. Chemical bond
Explanation: A chemical bond is the attractive force that binds atoms together to form molecules or compounds.
2. According to the octet rule, atoms tend to gain, lose, or share electrons to achieve:
A. Eight electrons in their outermost shell
B. Exactly two electrons only
C. A neutral charge only
D. Maximum atomic mass
Answer: A. Eight electrons in their outermost shell
Explanation: The octet rule states that atoms are most stable when their outer shell contains eight electrons, resembling the electron configuration of noble gases.
3. A bond formed by the complete transfer of electrons from one atom to another is called a/an:
A. Ionic bond
B. Covalent bond
C. Coordinate bond only
D. Metallic bond
Answer: A. Ionic bond
Explanation: Ionic bonds form when electrons are completely transferred from one atom to another, resulting in oppositely charged ions attracting each other.
4. A bond formed by the mutual sharing of electron pairs between two atoms is called a:
A. Covalent bond
B. Ionic bond
C. Metallic bond
D. Hydrogen bond only
Answer: A. Covalent bond
Explanation: Covalent bonds are formed when two atoms share one or more pairs of electrons to achieve stability.
5. A covalent bond in which both shared electrons are donated by the same atom is called a:
A. Coordinate (dative) bond
B. Ionic bond
C. Polar covalent bond only
D. Metallic bond
Answer: A. Coordinate (dative) bond
Explanation: A coordinate or dative bond is a special type of covalent bond where one atom alone supplies both electrons of the shared pair.
6. The bond formed between highly electropositive metals and highly electronegative non-metals is typically:
A. Ionic
B. Covalent
C. Metallic only
D. Coordinate only
Answer: A. Ionic
Explanation: The large electronegativity difference between metals and non-metals favours complete electron transfer, forming an ionic bond.
7. A covalent bond formed by the sharing of a single pair of electrons is called a:
A. Single bond
B. Double bond
C. Triple bond
D. Coordinate bond only
Answer: A. Single bond
Explanation: A single bond involves the sharing of just one pair of electrons between two bonded atoms.
8. A covalent bond formed by the sharing of two pairs of electrons is called a:
A. Double bond
B. Single bond
C. Triple bond
D. Ionic bond
Answer: A. Double bond
Explanation: A double bond involves the sharing of two electron pairs between the bonded atoms, resulting in a stronger and shorter bond than a single bond.
9. A covalent bond formed by the sharing of three pairs of electrons is called a:
A. Triple bond
B. Single bond
C. Double bond
D. Coordinate bond
Answer: A. Triple bond
Explanation: A triple bond involves the sharing of three electron pairs, making it the strongest and shortest type of covalent bond among the three.
10. The theory that predicts the geometry of molecules based on the repulsion between electron pairs around a central atom is called:
A. VSEPR theory
B. Valence bond theory
C. Molecular orbital theory
D. Octet theory
Answer: A. VSEPR theory
Explanation: VSEPR (Valence Shell Electron Pair Repulsion) theory predicts molecular shapes based on minimising repulsion between electron pairs surrounding the central atom.
11. According to VSEPR theory, lone pairs of electrons generally cause:
A. Greater repulsion than bonded pairs, affecting molecular geometry
B. No effect on molecular geometry
C. Less repulsion than bonded pairs
D. Only attraction between atoms
Answer: A. Greater repulsion than bonded pairs, affecting molecular geometry
Explanation: Lone pairs occupy more space and exert greater repulsive force than bonding pairs, often distorting the ideal molecular geometry.
12. The mixing of atomic orbitals to form new hybrid orbitals of equal energy is called:
A. Hybridisation
B. Resonance
C. Polarisation
D. Ionisation
Answer: A. Hybridisation
Explanation: Hybridisation describes the process where atomic orbitals combine to form new, equivalent hybrid orbitals used in bonding.
13. The hybridisation involving one s and one p orbital, resulting in a linear geometry, is called:
A. sp hybridisation
B. sp² hybridisation
C. sp³ hybridisation
D. sp³d hybridisation
Answer: A. sp hybridisation
Explanation: sp hybridisation combines one s and one p orbital, producing two hybrid orbitals arranged linearly at 180°.
14. The hybridisation involving one s and two p orbitals, resulting in a trigonal planar geometry, is called:
A. sp² hybridisation
B. sp hybridisation
C. sp³ hybridisation
D. sp³d² hybridisation
Answer: A. sp² hybridisation
Explanation: sp² hybridisation combines one s and two p orbitals, forming three hybrid orbitals arranged in a trigonal planar shape at 120°.
15. The hybridisation involving one s and three p orbitals, resulting in a tetrahedral geometry, is called:
A. sp³ hybridisation
B. sp² hybridisation
C. sp hybridisation
D. sp³d hybridisation
Answer: A. sp³ hybridisation
Explanation: sp³ hybridisation combines one s and three p orbitals, producing four equivalent hybrid orbitals arranged tetrahedrally at approximately 109.5°.
16. A molecule in which the actual structure is a blend of two or more possible Lewis structures is said to exhibit:
A. Resonance
B. Hybridisation only
C. Polarisation only
D. Ionisation only
Answer: A. Resonance
Explanation: Resonance occurs when a molecule's true structure cannot be represented by a single Lewis structure and is instead a hybrid of multiple contributing structures.
17. A covalent bond between two atoms with different electronegativities, resulting in unequal sharing of electrons, is called a:
A. Polar covalent bond
B. Non-polar covalent bond
C. Ionic bond
D. Metallic bond
Answer: A. Polar covalent bond
Explanation: In a polar covalent bond, the more electronegative atom attracts the shared electron pair more strongly, creating partial positive and negative charges.
18. A covalent bond between two identical atoms, resulting in equal sharing of electrons, is called a:
A. Non-polar covalent bond
B. Polar covalent bond
C. Ionic bond
D. Coordinate bond
Answer: A. Non-polar covalent bond
Explanation: Non-polar covalent bonds form between atoms of equal electronegativity, resulting in an even distribution of the shared electron pair.
19. The attractive force between a hydrogen atom bonded to a highly electronegative atom and another electronegative atom is called a:
A. Hydrogen bond
B. Ionic bond
C. Covalent bond
D. Metallic bond
Answer: A. Hydrogen bond
Explanation: Hydrogen bonding is a special type of dipole-dipole attraction occurring when hydrogen is bonded to highly electronegative atoms like O, N or F.
20. Molecular orbital theory describes bonding in terms of the combination of atomic orbitals to form:
A. Molecular orbitals
B. Only ionic pairs
C. Only lone pairs
D. Hybridised atoms
Answer: A. Molecular orbitals
Explanation: Molecular orbital theory explains chemical bonding by describing how atomic orbitals combine to form new molecular orbitals spanning the entire molecule.
21. Bonding molecular orbitals are generally:
A. Lower in energy than the combining atomic orbitals
B. Higher in energy than the atomic orbitals
C. Equal in energy to atomic orbitals
D. Non-existent in real molecules
Answer: A. Lower in energy than the combining atomic orbitals
Explanation: Bonding molecular orbitals form at a lower energy level than the original atomic orbitals, contributing to overall molecular stability.
22. Antibonding molecular orbitals are generally:
A. Higher in energy than the combining atomic orbitals
B. Lower in energy than atomic orbitals
C. Equal in energy to atomic orbitals
D. Non-existent in molecules
Answer: A. Higher in energy than the combining atomic orbitals
Explanation: Antibonding molecular orbitals possess higher energy than the original atomic orbitals, and their occupation generally destabilises the molecule.
23. The bond order in molecular orbital theory is calculated as half the difference between the number of electrons in:
A. Bonding and antibonding orbitals
B. Only bonding orbitals
C. Only antibonding orbitals
D. Only lone pairs
Answer: A. Bonding and antibonding orbitals
Explanation: Bond order = 1/2 (number of bonding electrons - number of antibonding electrons), indicating the overall strength and stability of the bond.
24. The shape of a water molecule (H₂O), according to VSEPR theory, is:
A. Bent (angular)
B. Linear
C. Tetrahedral
D. Trigonal planar
Answer: A. Bent (angular)
Explanation: Due to the two lone pairs on oxygen repelling the bonding pairs, the water molecule adopts a bent or angular shape.
25. The shape of a methane molecule (CH₄), according to VSEPR theory, is:
A. Tetrahedral
B. Linear
C. Bent
D. Trigonal planar
Answer: A. Tetrahedral
Explanation: With four bonding pairs and no lone pairs around the central carbon atom, methane adopts a symmetrical tetrahedral shape.
26. Ionic compounds generally have high melting and boiling points due to:
A. Strong electrostatic forces of attraction between ions
B. Weak van der Waals forces
C. Covalent sharing of electrons
D. Metallic bonding
Answer: A. Strong electrostatic forces of attraction between ions
Explanation: The strong electrostatic attraction between oppositely charged ions in an ionic lattice requires significant energy to overcome, resulting in high melting points.
27. Metallic bonding involves a 'sea of electrons' that are:
A. Delocalised and free to move throughout the metal lattice
B. Fixed to individual atoms
C. Completely absent in metals
D. Transferred entirely to one atom
Answer: A. Delocalised and free to move throughout the metal lattice
Explanation: Metallic bonding is characterised by delocalised electrons that move freely throughout the metallic lattice, contributing to properties like conductivity.
28. The overlapping of atomic orbitals along the internuclear axis forms a:
A. Sigma (σ) bond
B. Pi (π) bond
C. Delta bond
D. Ionic bond
Answer: A. Sigma (σ) bond
Explanation: A sigma bond results from the head-on overlap of atomic orbitals directly along the axis connecting the two nuclei.
29. The sideways overlapping of parallel atomic orbitals forms a:
A. Pi (π) bond
B. Sigma (σ) bond
C. Ionic bond
D. Metallic bond
Answer: A. Pi (π) bond
Explanation: A pi bond forms from the lateral (sideways) overlap of parallel p-orbitals, typically found in double and triple bonds alongside a sigma bond.
30. Dipole moment is a measure of the:
A. Polarity of a bond or molecule
B. Total number of bonds present
C. Total mass of a molecule
D. Number of lone pairs only
Answer: A. Polarity of a bond or molecule
Explanation: Dipole moment quantifies the extent of charge separation within a polar bond or molecule, reflecting its overall polarity.
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