MCQ 31
The energy of an electron in an atom is quantized. What does this mean?
A) Electrons can have any energy.
B) Electrons have discrete energy levels.
C) Electrons can exist in two states at once.
D) Electrons are stationary.
Answer: B) Electrons have discrete energy levels.
Explanation: Quantization of energy means that electrons can only exist in specific energy levels, rather than any value.
MCQ 32
Which of the following phenomena is explained by the wave nature of electrons?
A) Photoelectric effect
B) Atomic stability
C) Chemical bonding
D) Ionization energy
Answer: A) Photoelectric effect.
Explanation: The photoelectric effect demonstrates the wave-particle duality of light and is explained by considering light as a wave and a stream of photons.
MCQ 33
What is the correct electron configuration for sulfur (atomic number 16)?
A) 1s² 2s² 2p⁶ 3s² 3p⁴
B) 1s² 2s² 2p⁶ 3s² 3p³
C) 1s² 2s² 2p⁶ 3s² 3p²
D) 1s² 2s² 2p⁶ 3s² 4p²
Answer: A) 1s² 2s² 2p⁶ 3s² 3p⁴.
Explanation: Sulfur has 16 electrons, filling the orbitals up to 3p, which has four electrons.
MCQ 34
What occurs when an electron transitions from a higher energy level to a lower one?
A) Absorption of energy
B) Emission of energy
C) Ionization
D) Excitation
Answer: B) Emission of energy.
Explanation: When an electron drops from a higher energy level to a lower one, it emits energy in the form of a photon.
MCQ 35
The term “ionic bond” refers to:
A) A bond formed by the sharing of electrons.
B) A bond formed by the transfer of electrons.
C) A bond with a partial charge.
D) A covalent bond with multiple shared pairs.
Answer: B) A bond formed by the transfer of electrons.
Explanation: An ionic bond is formed when one atom donates an electron to another, resulting in attraction between positively and negatively charged ions.
MCQ 36
Which of the following is a characteristic of covalent bonds?
A) High melting and boiling points.
B) Formed by the transfer of electrons.
C) Typically soluble in water.
D) Involves sharing of electrons.
Answer: D) Involves sharing of electrons.
Explanation: Covalent bonds involve the sharing of electron pairs between atoms, leading to the formation of molecules.
MCQ 37
What is the shape of a molecule with a tetrahedral arrangement of electron pairs?
A) Linear
B) Trigonal planar
C) Tetrahedral
D) Bent
Answer: C) Tetrahedral.
Explanation: A tetrahedral arrangement occurs when four electron pairs (bonding or lone pairs) are arranged around a central atom, leading to a three-dimensional tetrahedral shape.
MCQ 38
What is the primary factor that determines the shape of a molecule?
A) The number of protons.
B) The type of bonds formed.
C) The arrangement of electron pairs around the central atom.
D) The size of the atoms involved.
Answer: C) The arrangement of electron pairs around the central atom.
Explanation: The VSEPR theory states that the shape of a molecule is determined by the repulsions between electron pairs, including bonding and lone pairs.
MCQ 39
In which type of bond are electrons shared equally?
A) Ionic bond
B) Polar covalent bond
C) Nonpolar covalent bond
D) Metallic bond
Answer: C) Nonpolar covalent bond.
Explanation: In a nonpolar covalent bond, electrons are shared equally between atoms, typically between identical atoms or those with similar electronegativities.
MCQ 40
What is the hybridization of a carbon atom in ethylene (C₂H₄)?
A) sp
B) sp²
C) sp³
D) sp³d
Answer: B) sp².
Explanation: In ethylene, each carbon atom is involved in a double bond with another carbon atom, leading to sp² hybridization, where one s and two p orbitals mix.
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