Engineering
Chemistry
Quantum Wave Mechanical Model

Question

The wave function ψn.ℓ,mℓ is a mathematical function whose value depends upon spherical polar coordinates (r,θ,φ) of the electron and characterized by the quantum numbers n,ℓ and mℓ. Here r is distance from nucleus, θ is colatitude and φ is azimuth. In the mathematical functions given in the Table, Z is atomic number and a0 is Bohr radius.

Column 1 Column 2 Column 3
(I) 1 s orbital  (i) Ψn,ℓ,mℓ∝(Za0)32e−(Zra0)
(II ) 2s orbital (ii) One radial node (Q) Probability density at nuvleus ∝1a03
(III) 2pz orbital  (iii) Ψ∝(Za0)52re−(Zrza0)cosθ  (R) Probability density is maximun at nucleus
(IV) 3dz2 orbital (iv) xy- plane is a nodal plane  

(S) Energy needed to excite electron from n=2 state to n=4 state is times the energy needed to excite electron from n=2 state

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Linked Question 1

For He+ ion, the only INCORRECT combination is

(II) (ii) (Q)

(I) (i) (R)

(I) (i) (S)

(I) (iii) (R)

Solution

For He+ ion

(A)        For 1s-orbital,    ψn, ℓ, mℓ∝(Za0)32.e−(Zra0)

            and probability density = |ψn,ℓ,mℓ|2

            s-orbital has no angular node.

            ∴ (I) (i) (R) is correct combination

(B)        For 2s-orbital. There us one radial node & ψn, ℓ, mℓ∝(Za0)32.e−(Zr2a0)

             ∴ Probability density∝1a03

             ∴ (II) (ii) (Q) is correct combination

(C)        For 1s-orbital : ψn,ℓ;mℓ∝(Za0)32.e−(Zra0)

             (ΔE2→4)He+= (–0.85 + 3.4) × 22 eV

             (ΔE2→4)He+=13.6×(14−136)×22eV       = (2.55 × 22 )eV

             = 3.022 × 22 eV

             ⇒2732 × 3.022 × 22 = 2.55 × 22

             ∴ (I) (i) (S) is correct combination

(D)        For 1s-orbital :  ψn,ℓ,mℓ∝(Za0)32.e−(Zra0)

             ∴ (I) (iii) are incorrect combination

             ∴ Answer (D)

Linked Question 2

For the given orbital in column 1, the only CORRECT combination for any hydrogen-like species is

(I) (ii) (S)

(III) (iii) (P)

(II) (ii) (P)

(IV) (iv) (R)

Solution

For 2s-orbital :

           Number of radial node = 1

           & probability density at nucleus = |ψn,ℓ,mℓ|2

           i.e. probability density at nucleus ∝1a03

           ∴ (II) (ii) (P) is incorrect combination

           ∴ Answer (D)

Linked Question 3

For hydrogen atom, the only CORRECT combination is

(I) (i) (S)

(II) (i) (Q)

(I) (iv) (R)

(I) (i) (P)

Solution

(D)        For 1s-orbital : ψn,ℓ,mℓ∝(Za0)32.e−(Zra0)

             (ΔE2→4)H = (–0.85 + 3.4) eV = 2.55 eV

             (ΔE2→6)H=13.6 (14−136)eV = 3.022

             But, 3.022 ×2732= 2.55

             ∴ (I) (i) (S) is correct combination

             ∴ Answer (D)