chemistry : class11 dz2 Orbital Shape : Shapes of d orbitals : Structure of Atom MCQ Questions and Answers
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dz2 Orbital Shape
MCQ questions and answers.
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MCQ Questions
1. Which description most accurately represents the three-dimensional shape of the d_z2 orbital?
A.
Four lobes lying in the xy-plane between the x- and y-axes
B.
Two elongated lobes along the z-axis with a doughnut-shaped torus around the nucleus in the xy-plane
C.
Two spherical lobes centered on the x- and y-axes
D.
A single spherical electron cloud concentrated around the nucleus
Correct Answer:
Two elongated lobes along the z-axis with a doughnut-shaped torus around the nucleus in the xy-plane
Explanation:
The d_z2 orbital has two major lobes directed along the z-axis and a toroidal, or doughnut-shaped, region of electron density in the xy-plane around the nucleus.
2. In the d_z2 orbital, where is the characteristic doughnut-shaped region of electron density located?
A.
In a plane perpendicular to the z-axis and passing through the nucleus
B.
In a plane containing the z-axis and the x-axis
C.
In two planes passing through the xz- and yz-axes
D.
Along the z-axis between the two principal lobes
Correct Answer:
In a plane perpendicular to the z-axis and passing through the nucleus
Explanation:
The torus of the d_z2 orbital surrounds the nucleus in the xy-plane, which is perpendicular to the z-axis and passes through the nucleus.
3. Which statement correctly distinguishes the d_z2 orbital from the other four d orbitals in terms of its visual shape?
A.
It has four equivalent lobes directed between coordinate axes
B.
It has two lobes along the z-axis and an additional toroidal region around the nucleus
C.
It has only one lobe directed along the positive z-axis
D.
It has a spherical shape with no directional character
Correct Answer:
It has two lobes along the z-axis and an additional toroidal region around the nucleus
Explanation:
Unlike the four-lobed shapes of the other d orbitals, d_z2 consists of two z-axis lobes together with a torus in the xy-plane.
4. A student draws the d_z2 orbital as four lobes lying in the xy-plane. Which correction is necessary?
A.
The orbital should be redrawn with four lobes lying between the x- and y-axes
B.
The orbital should be redrawn as two lobes along the z-axis surrounded by a torus in the xy-plane
C.
The orbital should be redrawn as a sphere centered at the nucleus
D.
The orbital should be redrawn with two lobes along the x-axis and two along the y-axis
Correct Answer:
The orbital should be redrawn as two lobes along the z-axis surrounded by a torus in the xy-plane
Explanation:
The d_z2 orbital is oriented along the z-axis, not confined to the xy-plane. Its distinctive shape includes two z-directed lobes and a toroidal region in the xy-plane.
5. If the d_z2 orbital is viewed along the z-axis toward the nucleus, what feature is most characteristic of the view?
A.
Four distinct lobes arranged in a cross
B.
A circular toroidal region surrounding a central nodal point
C.
Two lobes separated by a vertical nodal plane
D.
A uniform spherical boundary with no central structure
Correct Answer:
A circular toroidal region surrounding a central nodal point
Explanation:
Looking along the z-axis, the torus in the xy-plane appears circular around the nucleus, while the two z-axis lobes are viewed end-on.
6. Which cross-sectional observation is consistent with the shape of the d_z2 orbital in the xz-plane?
A.
Two lobes along the z-axis with regions extending around the nucleus near the equatorial direction
B.
Four lobes confined entirely to the xz-plane and directed between its axes
C.
A single lobe centered at the origin and extending equally in all directions
D.
Two lobes along the x-axis with no density near the z-axis
Correct Answer:
Two lobes along the z-axis with regions extending around the nucleus near the equatorial direction
Explanation:
The xz-plane cuts through the two principal z-axis lobes and also intersects the toroidal region surrounding the nucleus near the equatorial direction.
7. Which statement about the directional distribution of the d_z2 orbital is correct?
A.
Its principal electron-density lobes point along the x- and y-axes
B.
Its principal electron-density lobes point along the z-axis, while the torus lies around the equatorial region
C.
Its electron density is concentrated only in the xy-plane
D.
Its electron density is distributed in four diagonal directions within the xy-plane
Correct Answer:
Its principal electron-density lobes point along the z-axis, while the torus lies around the equatorial region
Explanation:
The defining orientation of d_z2 is along the z-axis. The additional torus occupies the equatorial region around the nucleus in the xy-plane.
8. Which proposed sketch would represent the d_z2 orbital rather than the d_x2-y2 orbital?
A.
Four lobes directed along the positive and negative x- and y-axes
B.
Four lobes directed between the x- and y-axes
C.
Two lobes directed along the positive and negative z-axis with a ring-like region around the center
D.
Four lobes directed along the positive and negative x- and z-axes
Correct Answer:
Two lobes directed along the positive and negative z-axis with a ring-like region around the center
Explanation:
The d_z2 orbital is identified by its two z-axis lobes and central torus, whereas d_x2-y2 has four lobes along the x- and y-axes.
9. Why is the d_z2 orbital often described as having a dumbbell-and-doughnut shape?
A.
Its two z-axis lobes form the dumbbell, and its equatorial torus forms the doughnut
B.
Its two x-axis lobes form the dumbbell, and its y-axis lobes form the doughnut
C.
Its four xy-plane lobes collectively form a dumbbell and a spherical ring
D.
Its spherical electron cloud is compressed into a doughnut around the nucleus
Correct Answer:
Its two z-axis lobes form the dumbbell, and its equatorial torus forms the doughnut
Explanation:
The two elongated lobes on opposite sides of the nucleus along z resemble a dumbbell, while the surrounding xy-plane electron density forms a torus resembling a doughnut.
10. A diagram of an orbital shows rotational symmetry about the z-axis, two opposite lobes along that axis, and a torus centered on the nucleus. Which orbital shape does it depict?
A.
d_xy
B.
d_x2-y2
C.
d_yz
D.
d_z2
Correct Answer:
d_z2
Explanation:
The d_z2 orbital has rotational symmetry about the z-axis and uniquely combines two z-axis lobes with a torus centered in the xy-plane.