NEET 2025 MCQ with Answer Explanation : “Quantum Mechanical Model”

MCQ 91
Which of the following best describes a hydrocarbon?

A) A compound containing hydrogen and oxygen.
B) A compound containing only carbon and hydrogen.
C) A compound containing carbon, hydrogen, and nitrogen.
D) A compound containing carbon and sulfur.

Answer: B) A compound containing only carbon and hydrogen.

Explanation: Hydrocarbons are organic compounds made solely of hydrogen and carbon atoms.

MCQ 92
Which of the following is a characteristic of an endothermic reaction?

A) Releases heat.
B) Absorbs heat.
C) Produces gas only.
D) Occurs spontaneously.

Answer: B) Absorbs heat.

Explanation: Endothermic reactions absorb heat from their surroundings, resulting in a decrease in temperature.

MCQ 93
What type of bond is formed between sodium (Na) and chlorine (Cl) in sodium chloride (NaCl)?

A) Covalent bond
B) Ionic bond
C) Metallic bond
D) Hydrogen bond

Answer: B) Ionic bond.

Explanation: Sodium chloride (NaCl) is formed by the ionic bond resulting from the transfer of an electron from sodium to chlorine.

MCQ 94
Which of the following statements is true regarding the energy levels of an atom?

A) Energy levels are continuous.
B) Energy levels can only hold one electron.
C) Electrons in lower energy levels are more stable.
D) Energy levels have no influence on the atom’s chemical properties.

Answer: C) Electrons in lower energy levels are more stable.

Explanation: Electrons in lower energy levels are generally more stable due to being closer to the nucleus, where the attractive force is stronger.

MCQ 95
What is the shape of the p orbital?

A) Spherical
B) Dumbbell
C) Complex
D) Circular

Answer: B) Dumbbell.

Explanation: The p orbital has a characteristic dumbbell shape with two lobes.

MCQ 96
What is the term for the energy required to remove an electron from an atom?

A) Electron affinity
B) Ionization energy
C) Electronegativity
D) Activation energy

Answer: B) Ionization energy.

Explanation: Ionization energy is the energy needed to remove an electron from a gaseous atom or ion.

MCQ 97
What phenomenon is observed when light is passed through a prism?

A) Reflection
B) Diffraction
C) Dispersion
D) Absorption

Answer: C) Dispersion.

Explanation: Dispersion occurs when different wavelengths of light are separated as they pass through a prism, creating a spectrum.

MCQ 98
Which of the following is a consequence of the wave nature of electrons?

A) They have a definite position.
B) They exhibit interference patterns.
C) They can only exist in one energy state.
D) They do not interact with electromagnetic fields.

Answer: B) They exhibit interference patterns.

Explanation: The wave nature of electrons allows them to exhibit interference patterns, similar to light waves.

MCQ 99
What does the term “orbital” refer to in quantum chemistry?

A) A fixed path around the nucleus
B) A region of space where an electron is likely to be found
C) A particle with mass
D) An energy level of an atom

Answer: B) A region of space where an electron is likely to be found.

Explanation: An orbital describes the spatial distribution of an electron’s probability density around the nucleus.

MCQ 100
Which of the following elements has the largest atomic radius?

A) Helium (He)
B) Lithium (Li)
C) Sodium (Na)
D) Potassium (K)

Answer: D) Potassium (K).

Explanation: Atomic radius increases down a group in the periodic table due to the addition of electron shells, making potassium the largest among these elements.