chemistry : class11 Orbital Definition : Concept of orbitals : Structure of Atom MCQ Questions and Answers
Practice important
Orbital Definition
MCQ questions and answers.
Page 2
of
3
|
30
MCQ Questions
1. Which statement most precisely defines an atomic orbital?
A.
A fixed circular path followed by an electron around the nucleus
B.
A three-dimensional region in which the electron is most likely to be found
C.
The exact position and velocity of an electron at a particular instant
D.
The energy shell containing all electrons with the same principal quantum number
Correct Answer:
A three-dimensional region in which the electron is most likely to be found
Explanation:
An orbital is a three-dimensional region of space associated with a high probability of finding an electron. It is not a definite path or an exact electron trajectory.
2. In the quantum-mechanical description of an orbital, the quantity that directly represents the probability density of finding an electron is:
A.
The wave function, ψ
B.
The square of the wave function, ψ²
C.
The reciprocal of the wave function, 1/ψ
D.
The first derivative of the wave function, dψ/dr
Correct Answer:
The square of the wave function, ψ²
Explanation:
The wave function ψ describes the state of an electron, but its square, ψ², gives the probability density associated with finding the electron at a point in the orbital.
3. Why is an orbital not regarded as a definite path of electron motion?
A.
Because an orbital contains no information about electron energy
B.
Because the electron is distributed over a region described by probability rather than assigned a classical trajectory
C.
Because electrons remain permanently stationary inside orbitals
D.
Because orbitals exist only outside the influence of the nucleus
Correct Answer:
Because the electron is distributed over a region described by probability rather than assigned a classical trajectory
Explanation:
An orbital is a probability distribution obtained from the wave-mechanical description of an electron. It does not specify a classical path or trajectory.
4. Two orbitals may differ in their spatial orientation while having the same general type and energy in an isolated hydrogen atom. Which feature of the orbital definition accounts for this difference?
A.
An orbital is characterized only by the electron's mass
B.
An orbital includes a specific spatial probability distribution
C.
An orbital is defined as a circular orbit with a different radius
D.
An orbital is determined only by the total number of electrons in the atom
Correct Answer:
An orbital includes a specific spatial probability distribution
Explanation:
An orbital represents a particular spatial distribution of electron probability. Orbitals of the same type can have different orientations while retaining the same basic orbital character.
5. Which statement correctly distinguishes an orbital from an electron shell?
A.
An orbital is a single permitted region within a shell, whereas a shell is a collection of orbitals associated with a principal energy level
B.
An orbital is larger than every shell and contains several nuclei
C.
A shell is a path, whereas an orbital is the electron's exact position
D.
An orbital and a shell are identical terms with different symbols
Correct Answer:
An orbital is a single permitted region within a shell, whereas a shell is a collection of orbitals associated with a principal energy level
Explanation:
An orbital is an individual region of electron probability, while a shell is a broader principal energy level containing one or more subshells and orbitals.
6. What does a boundary surface drawn for an orbital usually represent?
A.
The exact physical surface of the electron
B.
A surface enclosing a specified high probability of finding the electron
C.
The outermost path on which the electron must move
D.
A surface on which the probability of finding the electron is always zero
Correct Answer:
A surface enclosing a specified high probability of finding the electron
Explanation:
Orbital boundary surfaces are visual aids. They enclose a chosen percentage of the total electron probability and do not represent a solid physical boundary.
7. At a point where the wave function of an electron is zero, what does the orbital description imply at that point?
A.
The electron has zero mass there
B.
The probability density of finding the electron there is zero
C.
The electron must be moving with maximum speed there
D.
The orbital ceases to exist everywhere else
Correct Answer:
The probability density of finding the electron there is zero
Explanation:
Since probability density is proportional to ψ², a zero value of ψ gives zero probability density at that point. Such locations are associated with nodes.
8. Which statement about the size of an orbital is most consistent with its definition?
A.
An orbital has a sharply defined outer radius identical for all electrons
B.
An orbital's apparent size depends on the probability percentage selected for representing it
C.
An orbital is always confined to the nucleus
D.
An orbital has no spatial extent because an electron is a point particle
Correct Answer:
An orbital's apparent size depends on the probability percentage selected for representing it
Explanation:
An orbital is a probability distribution that generally extends mathematically through space. Its displayed boundary and apparent size depend on the chosen probability cutoff.
9. Which interpretation of the statement 'an electron occupies an orbital' is scientifically correct?
A.
The electron travels along the boundary of the orbital
B.
The electron is confined to one geometrically fixed point inside the orbital
C.
The electron is described by a wave function whose probability distribution corresponds to that orbital
D.
The electron continuously traces the orbital's shape as a classical object
Correct Answer:
The electron is described by a wave function whose probability distribution corresponds to that orbital
Explanation:
Occupying an orbital means that the electron's quantum state is represented by the orbital wave function and its associated probability distribution, not that it follows a visible path.
10. Which statement best explains why an orbital can have a directional shape even though the electron does not follow a fixed route?
A.
The directionality belongs to the spatial distribution of probability, not to a classical electron trajectory
B.
The electron moves only along the long axis of the orbital
C.
The nucleus physically stretches the electron into the orbital shape
D.
The orbital shape is produced by the electron's fixed circular revolution
Correct Answer:
The directionality belongs to the spatial distribution of probability, not to a classical electron trajectory
Explanation:
Orbital shapes show how electron probability is distributed in space. A directional shape therefore describes probability density and does not imply a definite path of motion.