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Structure of Atom question

2017 · Shift 1 · Q17
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Structure of Atom question

2017 · Shift 1 · Q17

JEE AdvancedChemistryStructure of AtomMCQ+3 / −1
The wave function, ψn,1,m1{\psi _{n,1,{m_1}}}ψn,1,m1​​ is a mathematical function whose value depends upon spherical polar coordinates (r,θ,ϕ)\left( {r,\theta ,\phi } \right)(r,θ,ϕ) of the electron and characterized by the quantum numbers n,1n,1n,1 and m1{m_1}m1​. Here rrr is distance from nucleus, θ\thetaθ is colatitude and ϕ\phiϕ is azimuth. In the mathematical functions given in the table, ZZZ is atomic number and a0{a_0}a0​ is Bohr radius. JEE Advanced 2017 Paper 1 Offline Chemistry - Structure of Atom Question 11 English ComprehensionFor hydrogen atom, the only CORRECT combination is :
  1. A
    (I) (i) (S)
  2. B
    (II) (i) (Q)
  3. C
    (I) (i) (P)
  4. D
    (I) (iv) (R)
View written solutionFree

Correct answer: A

The user wants me to identify the correct combination of orbital, its wave function, and its properties from the given table for a hydrogen atom.

Step-by-Step Analysis:

We need to evaluate each option by checking the consistency of the three parts: the orbital name (Column 1), its mathematical wave function (Column 2), and its angular property (Column 3).

1. Analyze the components of the table:

  • Column 1 & 2 (Orbital and Wave Function):

    • (I) 1s orbital: The quantum numbers are n=1,l=0,ml=0n=1, l=0, m_l=0n=1,l=0,ml​=0. The wave function is ψ1s=R1,0(r)Y0,0(θ,ϕ)\psi_{1s} = R_{1,0}(r)Y_{0,0}(\theta, \phi)ψ1s​=R1,0​(r)Y0,0​(θ,ϕ). The radial part R1,0(r)∝e−Zr/a0R_{1,0}(r) \propto e^{-Zr/a_0}R1,0​(r)∝e−Zr/a0​ and the angular part Y0,0Y_{0,0}Y0,0​ is a constant. Thus, ψ1s∝e−Zr/a0\psi_{1s} \propto e^{-Zr/a_0}ψ1s​∝e−Zr/a0​. This matches (i).
    • (II) 2s orbital: The quantum numbers are n=2,l=0,ml=0n=2, l=0, m_l=0n=2,l=0,ml​=0. The wave function is ψ2s∝(2−Zra0)e−Zr/2a0\psi_{2s} \propto (2 - \frac{Zr}{a_0})e^{-Zr/2a_0}ψ2s​∝(2−a0​Zr​)e−Zr/2a0​. None of the functions in Column 2 match this form.
    • (III) 2p_z orbital: The quantum numbers are n=2,l=1,ml=0n=2, l=1, m_l=0n=2,l=1,ml​=0. The wave function is ψ2pz=R2,1(r)Y1,0(θ,ϕ)\psi_{2p_z} = R_{2,1}(r)Y_{1,0}(\theta, \phi)ψ2pz​​=R2,1​(r)Y1,0​(θ,ϕ). The radial part R2,1(r)∝re−Zr/2a0R_{2,1}(r) \propto r e^{-Zr/2a_0}R2,1​(r)∝re−Zr/2a0​ and the angular part Y1,0(θ,ϕ)∝cos⁡θY_{1,0}(\theta, \phi) \propto \cos\thetaY1,0​(θ,ϕ)∝cosθ. Thus, ψ2pz∝re−Zr/2a0cos⁡θ\psi_{2p_z} \propto r e^{-Zr/2a_0} \cos\thetaψ2pz​​∝re−Zr/2a0​cosθ. This matches (ii).
    • (IV) 3d_{z^2} orbital: The quantum numbers are n=3,l=2,ml=0n=3, l=2, m_l=0n=3,l=2,ml​=0. The wave function is ψ3dz2=R3,2(r)Y2,0(θ,ϕ)\psi_{3d_{z^2}} = R_{3,2}(r)Y_{2,0}(\theta, \phi)ψ3dz2​​=R3,2​(r)Y2,0​(θ,ϕ). The radial part R3,2(r)∝r2e−Zr/3a0R_{3,2}(r) \propto r^2 e^{-Zr/3a_0}R3,2​(r)∝r2e−Zr/3a0​ and the angular part Y2,0(θ,ϕ)∝(3cos⁡2θ−1)Y_{2,0}(\theta, \phi) \propto (3\cos^2\theta - 1)Y2,0​(θ,ϕ)∝(3cos2θ−1). Thus, ψ3dz2∝r2e−Zr/3a0(3cos⁡2θ−1)\psi_{3d_{z^2}} \propto r^2 e^{-Zr/3a_0} (3\cos^2\theta - 1)ψ3dz2​​∝r2e−Zr/3a0​(3cos2θ−1). This matches (iv).
  • Column 3 (Angular Properties):

    • (P) ∝cos⁡θ\propto \cos\theta∝cosθ: This describes the angular dependence of a pzp_zpz​ orbital (l=1,ml=0l=1, m_l=0l=1,ml​=0).
    • (Q) Probability density is maximum on xy plane: This is true for orbitals like px,py,dx2−y2,dxyp_x, p_y, d_{x^2-y^2}, d_{xy}px​,py​,dx2−y2​,dxy​. The probability density for s,pz,dz2s, p_z, d_{z^2}s,pz​,dz2​ orbitals is not maximum on the xy plane.
    • (R) Probability density is constant on the surface r=constantr = constantr=constant: This means the probability density is spherically symmetric, which is a property of s-orbitals (l=0l=0l=0).
    • (S) Probability density is independent of azimuth angle ϕ\phiϕ: This means the wave function's angular part depends only on θ\thetaθ, not ϕ\phiϕ. This is true for all orbitals with magnetic quantum number ml=0m_l=0ml​=0 (e.g., s-orbitals, pzp_zpz​, dz2d_{z^2}dz2​). The probability density ∣ψ∣2|\psi|^2∣ψ∣2 will also be independent of ϕ\phiϕ.

2. Evaluate the given options:

  • Option A: (I) (i) (S)

    • (I) 1s orbital is correctly described by the wave function (i) ψ∝e−Zr/a0\psi \propto e^{-Zr/a_0}ψ∝e−Zr/a0​. The pairing (I)-(i) is correct.
    • For a (I) 1s orbital, the wave function is spherically symmetric, meaning it depends only on rrr. Therefore, its probability density ∣ψ∣2|\psi|^2∣ψ∣2 is independent of both θ\thetaθ and ϕ\phiϕ. The statement (S) Probability density is independent of azimuth angle ϕ\phiϕ is true for a 1s orbital.
    • All three parts of this combination are consistent. This option is correct.
  • Option B: (II) (i) (Q)

    • (II) 2s orbital is NOT described by the wave function (i) ψ∝e−Zr/a0\psi \propto e^{-Zr/a_0}ψ∝e−Zr/a0​, which is for the 1s orbital.
    • The pairing (II)-(i) is incorrect. This option is incorrect.
  • Option C: (I) (i) (P)

    • (I) 1s orbital is correctly described by the wave function (i). The pairing (I)-(i) is correct.
    • However, the property (P) ∝cos⁡θ\propto \cos\theta∝cosθ describes a pzp_zpz​ orbital, not a spherically symmetric 1s orbital.
    • The pairing (I)-(P) is incorrect. This option is incorrect.
  • Option D: (I) (iv) (R)

    • (I) 1s orbital is NOT described by the wave function (iv) ψ∝r2e−Zr/3a0(3cos⁡2θ−1)\psi \propto r^2 e^{-Zr/3a_0} (3\cos^2\theta - 1)ψ∝r2e−Zr/3a0​(3cos2θ−1), which is for the 3dz23d_{z^2}3dz2​ orbital.
    • The pairing (I)-(iv) is incorrect. This option is incorrect.

Conclusion:

Based on the analysis, only option A presents a fully correct and consistent combination of an orbital, its wave function, and its properties.

Final Answer is A.

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