The concept that contradicts the Bohr Model of an atom is: 

1.	Rutherford Model	2.	Heisenberg's Uncertainty Principle
3.	J.J. Thomson Model	4.	Photoelectric Effect

Electrons are emitted with zero velocity from a metal surface when it is exposed to radiation of wavelength 6800 Å. The work function (W₀) of the metal is: 

1. 3.109 × 10^–20 J

2. 2.922 × 10^–19 J

3. 4.031 × 10¹⁹ J

4. 2.319 × 10^–18 J

Determine the maximum number of emission lines produced when an electron in a hydrogen atom transitions from the n = 6  energy level to the ground state :

1. 30

2. 21

3. 15

4. 28

The ionization energy for H atom in the ground state is \(2.18 \times10^{-18}~ \mathrm J.\) The process energy requirements will be: \(( He^+(g) \rightarrow He^{2+}(g) + e^- )\)

Calculate the work function of silver metal, given that a stopping voltage of 0.35 eV is applied and the radiation has a wavelength of 256.7 nm.

1. 3.40 eV

2. 5.18 eV

3. 4.48 eV

4. –4.40 eV

Property which is same for the following species is:

 N^3–, O^2–, F^–, Na⁺, Mg²⁺ and Al³⁺ 

1. Ionic radii

2. Number of electrons

3. Nuclear charge

4. None of the above 

The number of radial nodes of 3s and 2p-orbitals are respectively:

(1) 2,0

(2) 0,2

(3) 1,2 

(4) 2,1

The wavelength of the radiation emitted when in a H atom, the electron falls from infinity to stationary state (n=1), is:

1. $15$ $nm$

2. 192 nm

3. 406 nm

4. 91 nm

The number of electrons with the azimuthal quantum number l = 1 and 2 for Cr ₂₄ in ground state is

1. 16 and 5

2. 12 and 5

3. 16 and 4

4. 12 and 4

Which of the following ions has the same radius as the first Bohr orbit of the hydrogen atom?

1. ${\mathrm{He}}^{+},$ $n=2$

2. ${\mathrm{Li}}^{2+},n=2$

3. ${\mathrm{Be}}^{3+},$ $n=2$

4. ${\mathrm{Li}}^{2+},\mathrm{n}=3$