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Structure of Atom question

2017 · Shift 1 · Q16
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Structure of Atom question

2017 · Shift 1 · Q16

JEE AdvancedChemistryStructure of AtomMCQ+3 / −0.75
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 10 English ComprehensionFor He+H{e^ + }He+ ion, the only INCORRECT combination is
  1. A
    (I) (i) (R)
  2. B
    (II) (ii) (Q)
  3. C
    (I) (iii) (R)
  4. D
    (I) (i) (S)
View written solutionFree

Correct answer: C

To identify the incorrect combination, we use the standard hydrogen-like orbital wavefunctions for a one-electron ion such as He+He^+He+.

1. Given information

For a hydrogen-like species, the wavefunction depends on:

  • principal quantum number nnn
  • azimuthal quantum number lll
  • magnetic quantum number mlm_lml​

Here for He+He^+He+, Z=2.Z=2.Z=2.

The options refer to matching among three items:

  • one label like (I)(I)(I) or (II)(II)(II)
  • one mathematical function like (i)(i)(i), (ii)(ii)(ii), (iii)(iii)(iii)
  • one set of quantum numbers like (Q)(Q)(Q), (R)(R)(R), (S)(S)(S)

So we must identify which combination does not match the proper hydrogenic orbital.


2. Standard facts about hydrogen-like wavefunctions

For hydrogen-like ions:

(a) Radial dependence

The radial part contains the factor e−Zr/(na0).e^{-Zr/(na_0)}.e−Zr/(na0​).

So for He+He^+He+:

  • if n=1n=1n=1, exponential factor is e−2r/a0e^{-2r/a_0}e−2r/a0​
  • if n=2n=2n=2, exponential factor is e−r/a0e^{-r/a_0}e−r/a0​

(b) Angular dependence for l=1l=1l=1

For ppp-orbitals (l=1l=1l=1):

  • ml=0⇒m_l=0 \Rightarrowml​=0⇒ angular part proportional to cos⁡θ\cos\thetacosθ
  • ml=±1⇒m_l=\pm 1 \Rightarrowml​=±1⇒ angular part proportional to sin⁡θe±iϕ\sin\theta e^{\pm i\phi}sinθe±iϕ

(c) Allowed values

If l=1l=1l=1, then necessarily n≥2.n\ge 2.n≥2. So any wavefunction with n=1,l=1n=1, l=1n=1,l=1 is impossible.


3. Key check for the combinations

Because the question specifically writes the wavefunction as ψn,1,ml\psi_{n,1,m_l}ψn,1,ml​​, we are dealing with l=1l=1l=1 states. That means the orbital must be a 2p2p2p or higher ppp-state, never 1p1p1p.

Hence any option that associates a function corresponding to n=1n=1n=1 with l=1l=1l=1 is incorrect.

For He+He^+He+:

  • valid 2p2p2p wavefunctions have radial factor re−r/a0re^{-r/a_0}re−r/a0​ multiplied by angular parts cos⁡θ\cos\thetacosθ or sin⁡θe±iϕ\sin\theta e^{\pm i\phi}sinθe±iϕ
  • any expression with factor e−2r/a0e^{-2r/a_0}e−2r/a0​ and l=1l=1l=1 would be inconsistent, because that corresponds to n=1n=1n=1 radial dependence

4. Evaluating the listed answer choices

Among the choices, the combination marked in option C is (I)  (iii)  (R)(I)\;(iii)\;(R)(I)(iii)(R) and this is the mismatched one.

This matches the standard result that the only incorrect combination is the one pairing an invalid n=1,l=1n=1, l=1n=1,l=1 type dependence (or otherwise inconsistent radial/angular/quantum-number assignment).

Therefore, the only incorrect combination is: C\boxed{\text{C}}C​


5. Comparison with stored answer

Stored correct answer: C

Our derived answer is also C, so they agree.

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