chemistry : class11 Subshell shapes : Concept of subshells : Structure of Atom MCQ Questions and Answers
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Subshell shapes
MCQ questions and answers.
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MCQ Questions
1. Which statement correctly distinguishes the shapes of the 2s and 2p subshells?
A.
Both are spherical, but the 2p subshell has a higher electron density at the nucleus
B.
The 2s subshell is spherical, whereas the 2p subshell has a dumbbell-shaped angular distribution
C.
The 2s subshell is dumbbell-shaped, whereas the 2p subshell is spherical
D.
Both have dumbbell-shaped distributions, but they differ only in orientation
Correct Answer:
The 2s subshell is spherical, whereas the 2p subshell has a dumbbell-shaped angular distribution
Explanation:
An s subshell has a spherically symmetric electron distribution, while a p subshell has two-lobed, dumbbell-shaped orbitals caused by its angular dependence.
2. For a real 2p orbital oriented along the z-axis, which nodal feature is necessarily associated with its shape?
A.
A spherical nodal surface centered on the nucleus
B.
A nodal plane coinciding with the xy-plane
C.
Two nodal planes coinciding with the xz- and yz-planes
D.
A toroidal nodal surface surrounding the nucleus
Correct Answer:
A nodal plane coinciding with the xy-plane
Explanation:
The pz orbital has two lobes along the z-axis and zero electron probability in the xy-plane, which is its angular nodal plane.
3. Which pair correctly identifies the nodal planes of the real dxy orbital?
A.
The xy-plane and the yz-plane
B.
The xz-plane and the yz-plane
C.
The xy-plane and a plane containing the z-axis at 45° to the x-axis
D.
Two planes perpendicular to the z-axis
Correct Answer:
The xz-plane and the yz-plane
Explanation:
The dxy orbital has lobes between the x- and y-axes. Its wavefunction becomes zero when x = 0 or y = 0, corresponding to the yz- and xz-planes.
4. In a coordinate system fixed to the nuclei, how does the shape of the real dx2-y2 orbital differ from that of the dxy orbital?
A.
dx2-y2 has lobes along the x- and y-axes, whereas dxy has lobes between these axes
B.
dx2-y2 has lobes along the z-axis, whereas dxy has lobes in the xy-plane
C.
dx2-y2 is spherical, whereas dxy is dumbbell-shaped
D.
dx2-y2 has a toroidal shape, whereas dxy has four planar lobes
Correct Answer:
dx2-y2 has lobes along the x- and y-axes, whereas dxy has lobes between these axes
Explanation:
The angular factor for dx2-y2 is proportional to x² − y², producing four lobes along the x and y axes. The dxy orbital is proportional to xy and therefore has lobes between those axes.
5. Which description best represents the characteristic shape of the dz2 orbital?
A.
Four lobes lying between the x- and y-axes in the xy-plane
B.
Two lobes along the z-axis accompanied by a toroidal region around the nucleus in the xy-plane
C.
Two lobes along the x-axis with a nodal plane parallel to the yz-plane
D.
A spherical region with two radial nodes
Correct Answer:
Two lobes along the z-axis accompanied by a toroidal region around the nucleus in the xy-plane
Explanation:
The dz2 orbital is commonly represented by two z-directed lobes and a doughnut-shaped, or toroidal, region around the nucleus in the xy-plane.
6. A subshell contains orbitals whose angular shapes are identical in form but differently oriented in space. Which subshell does this description most directly represent?
A.
The p subshell, whose three orbitals are oriented along mutually perpendicular axes
B.
The s subshell, whose orbitals have different spatial orientations
C.
The d subshell, whose orbitals are all spherical
D.
The f subshell, whose orbitals all have only one orientation
Correct Answer:
The p subshell, whose three orbitals are oriented along mutually perpendicular axes
Explanation:
The three p orbitals have the same dumbbell form but are oriented along the x, y, and z axes, respectively. Their differing orientations do not represent different basic angular shapes.
7. Which comparison of the five d orbitals is correct when considering their angular shapes?
A.
All five are spherical but differ in radial size
B.
Four have four-lobed forms, while dz2 has two lobes and a toroidal component
C.
Three are dumbbell-shaped and two are spherical
D.
All five have identical two-lobed shapes oriented along different axes
Correct Answer:
Four have four-lobed forms, while dz2 has two lobes and a toroidal component
Explanation:
The dxy, dyz, dxz, and dx2-y2 orbitals have four-lobed angular distributions. The dz2 orbital is distinctive because its shape includes two axial lobes and a torus.
8. Which statement about the angular nodal structure of subshells is consistent with their shapes?
A.
An s orbital has one angular nodal plane because it is spherical
B.
A p orbital has no angular node because its two lobes are connected
C.
A d orbital has two angular nodes, leading to more complex shapes than p orbitals
D.
All orbitals in a subshell have different numbers of angular nodes
Correct Answer:
A d orbital has two angular nodes, leading to more complex shapes than p orbitals
Explanation:
The number of angular nodes equals the azimuthal quantum number. Thus s, p, and d orbitals have zero, one, and two angular nodes, respectively, producing increasingly complex angular shapes.
9. If the coordinate axes are rotated without changing the physical atom, what happens to the apparent orientation of a real p orbital?
A.
Its spherical shape becomes a d-shaped orbital
B.
Its angular distribution can be described along the newly chosen axis, while its physical character remains p-like
C.
It loses its nodal plane because coordinate rotation changes the electron distribution
D.
It becomes an s orbital because all axes are equivalent
Correct Answer:
Its angular distribution can be described along the newly chosen axis, while its physical character remains p-like
Explanation:
The orientation labels px, py, and pz depend on the selected coordinate axes. Rotating the axes changes the description of orientation, not the underlying p-subshell shape or angular character.
10. Which option correctly relates the visible lobes of a real orbital to regions of electron probability?
A.
Each lobe represents a separate electron permanently localized in that region
B.
The lobes indicate regions of high probability density, while nodal surfaces are regions of zero probability
C.
The lobes indicate regions of zero probability, and the spaces between them contain the electron
D.
The number of lobes always equals the number of electrons allowed in the orbital
Correct Answer:
The lobes indicate regions of high probability density, while nodal surfaces are regions of zero probability
Explanation:
Orbital shapes represent the spatial distribution of probability density. Lobes are regions where finding an electron is more probable, whereas nodal surfaces have zero probability density.