Electromagnetic radiation of wavelength 242 nm is just sufficient to ionise sodium atom. The ionisation energy of sodium in kJ mol^-1 is -

1. 494

2. 4.94

3. 516

4. 0.50

A 25-watt bulb emits monochromatic yellow light with a wave length of 0.57µm. The rate of emission of quanta per second would be
$1. 7.17 \times {10}^{-19} {\mathrm{s}}^{-1}$
2. 4.13 × 10¹⁶ s^-1
3. 7.17 × 10¹⁹ s^-1
4. 1.26 × 10²⁰ s^-1

The wavelength of light emitted when the electron in a H atom undergoes the transition from an energy level with n = 4 to an energy level with n = 2, is 

1. 586 mm

2. 486 nm

3. 523 nm

4. 416 pm

The energy associated with the fifth orbit of a hydrogen atom is 

$$\begin{gathered} 1. -2.18 \times {10}^{-18} \mathrm{J} \\ 2. -8.72 \times {10}^{-20 }\mathrm{J} \\ 3. -3.88 \times {10}^{-21} \mathrm{J} \\ 4. -8.72 \times {10}^{-19} \mathrm{J} \end{gathered}$$

The wave number for the longest wavelength transition in the Balmer series of atomic hydrogen would be -

$$\begin{gathered} 1. 1.52 \times {10}^6 {\mathrm{m}}^{-1} \\ 2. 3.14 \times {10}^6 {\mathrm{cm}}^{-1} \\ 3. 15.2 \times {10}^6 {\mathrm{m}}^{-1} \\ 4. 1.52 \times {10}^6 {\mathrm{cm}}^{-1} \end{gathered}$$

The energy of an electron in H - atom is given by E_n = $\frac{(–2.18 \times {10}^{-18} )}{{\mathrm{n}}^2}$ J.  The shortest wavelength of light that can be used to remove an electron completely from n = 2 orbit will be

$$\begin{gathered} 1. 3647 \stackrel{°}{\mathrm{A}} \\ 2. 5132 \stackrel{°}{\mathrm{A}} \\ 3. 3017 \stackrel{°}{\mathrm{A}} \\ 4. \mathrm{None} \mathrm{of} \mathrm{these} \end{gathered}$$

The wavelength of an electron moving with a velocity of 2.05 × 10⁷ m s^-1  would be 

$1. 4.65 \times {10}^{-12 }\mathrm{m}$
2. 3.55 × 10^-11 m
3. 2.34 × 10¹¹ m
4. 6.43 × 10^-11 m

The kinetic energy of an electron is 3.0 × 10^–25 J. Its wave length would be 

1. 8.96 × 10^-7 m
2. 4.37 × 10^-6 m
3. 1.32 × 10^-7 m
4. 2.89 × 10^-4 m

The lowest value of n for 'g' orbitals is 

1. 4

2. 5

3. 3

4. 1

An atom of an element contains 29 electrons and 35 neutrons. The number of protons in the element would be

1. 29

2. 35

3. 6

4. 64