chemistry : class11 Orbital Shape : Concept of orbitals : Structure of Atom MCQ Questions and Answers
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Orbital Shape
MCQ questions and answers.
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MCQ Questions
1. For a 2p_x orbital, which statement correctly describes its angular shape and nodal plane?
A.
It has two lobes along the x-axis and a nodal plane represented by yz
B.
It has two lobes along the y-axis and a nodal plane represented by xz
C.
It has four lobes lying between the x- and y-axes and two nodal planes
D.
It is spherical with no angular nodal plane
Correct Answer:
It has two lobes along the x-axis and a nodal plane represented by yz
Explanation:
The 2p_x orbital has two oppositely phased lobes directed along the x-axis. Its wavefunction is zero wherever x = 0, which is the yz plane; this plane is its angular node.
2. Which description best distinguishes the shape of a d_z² orbital from that of the other four d orbitals?
A.
It consists of four lobes directed between the x- and y-axes
B.
It consists of two lobes along the z-axis accompanied by a toroidal region around the nucleus
C.
It consists of two spherical shells separated by a nodal plane
D.
It consists of four lobes directed along the x- and y-axes with no additional region
Correct Answer:
It consists of two lobes along the z-axis accompanied by a toroidal region around the nucleus
Explanation:
The d_z² orbital has two elongated lobes along the z-axis and a doughnut-shaped, or toroidal, region in the xy plane. This shape is different from the four-lobed cloverleaf shape of the other d orbitals.
3. The d_xy orbital has zero electron probability in which two planes?
A.
The xy plane and the xz plane
B.
The yz plane and the xy plane
C.
The xz plane and the yz plane
D.
The planes defined by x = y and x = -y
Correct Answer:
The xz plane and the yz plane
Explanation:
The d_xy orbital has lobes between the x- and y-axes. Its wavefunction is zero when x = 0 or y = 0, corresponding to the yz and xz planes, respectively.
4. Which statement correctly describes the orientation of the four lobes of a d_x²−y² orbital?
A.
The lobes point along the x- and y-axes, and the nodal planes are xz and yz
B.
The lobes lie between the x- and y-axes, and the nodal planes are xz and yz
C.
The lobes point along the z-axis, with a torus in the xy plane
D.
The lobes lie between the x- and y-axes, with nodal planes represented by x = y and x = -y
Correct Answer:
The lobes point along the x- and y-axes, and the nodal planes are xz and yz
Explanation:
For d_x²−y², the angular part of the wavefunction is proportional to x² − y². The lobes therefore lie along the x- and y-axes, while the wavefunction becomes zero in the xz and yz planes.
5. Two orbitals have the same principal quantum number and angular momentum quantum number but differ only in their magnetic quantum numbers. What property must they share?
A.
They must have identical spatial orientation
B.
They must have the same general type of angular shape but may have different orientations in space
C.
They must have different numbers of angular nodes
D.
They must both be spherical because their principal quantum numbers are equal
Correct Answer:
They must have the same general type of angular shape but may have different orientations in space
Explanation:
For a fixed angular momentum quantum number l, orbitals have the same general angular character and number of angular nodes. Different magnetic quantum numbers distinguish their orientations or linear combinations in space.
6. Which orbital has a cloverleaf shape with lobes lying between the coordinate axes rather than directly along them?
A.
d_x²−y²
B.
d_z²
C.
d_xy
D.
p_z
Correct Answer:
d_xy
Explanation:
The d_xy orbital has four lobes situated in the xy plane between the x- and y-axes. In contrast, d_x²−y² has its lobes directly along those axes.
7. A nodal plane of a p_y orbital is observed. Which equation describes this plane?
A.
x = 0
B.
y = 0
C.
z = 0
D.
x² + y² = z²
Correct Answer:
y = 0
Explanation:
The p_y orbital has lobes along the y-axis. Its wavefunction is proportional to y and becomes zero when y = 0, which defines the xz nodal plane.
8. Which comparison of 2p and 3p orbital shapes is correct when only their angular shape is considered?
A.
The 3p orbital is spherical, whereas the 2p orbital is dumbbell-shaped
B.
Both have the same dumbbell-shaped angular distribution, although their sizes and radial structures differ
C.
The 2p orbital has two angular nodes, whereas the 3p orbital has one
D.
The 3p orbital has a four-lobed angular shape because its principal quantum number is larger
Correct Answer:
Both have the same dumbbell-shaped angular distribution, although their sizes and radial structures differ
Explanation:
Both 2p and 3p orbitals have l = 1, so each has one angular node and a two-lobed, dumbbell-shaped angular distribution. Their radial extent and radial nodes differ, but their angular shape is the same.
9. Which orbital has lobes in the xz plane between the x- and z-axes and nodal planes represented by xy and yz?
A.
d_xy
B.
d_xz
C.
d_yz
D.
d_x²−y²
Correct Answer:
d_xz
Explanation:
The d_xz orbital has four lobes lying between the x- and z-axes in the xz plane. Its wavefunction is proportional to xz, so it vanishes when x = 0 or z = 0, giving the yz and xy nodal planes.
10. Which statement correctly relates the angular momentum quantum number l to the shape-related nodal structure of an orbital?
A.
An orbital with l = 0 has one angular node and a dumbbell shape
B.
An orbital with l = 1 has no angular nodes and a spherical shape
C.
An orbital with l = 2 has two angular nodes and generally displays d-orbital angular shapes
D.
An orbital with l = 3 has two angular nodes and always has a four-lobed shape
Correct Answer:
An orbital with l = 2 has two angular nodes and generally displays d-orbital angular shapes
Explanation:
The number of angular nodes equals l. Thus, l = 2 orbitals have two angular nodes and exhibit the characteristic angular shapes of d orbitals, including the four-lobed and d_z² forms.
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