With a certain exciting radiation of a particular frequency, to which hydrogen atoms are exposed, the maximum number of spectral lines obtainable in the emission is 15. The uppermost energy level to which the electron is excited is 

1. 4

2. 5

3. 6

4. 7

Consider an electron which is brought close to the nucleus of the atom from an infinite distance, the energy of the electron-nucleus system:

1. Increases

2. Decreases

3. Remains the same

4. None of these

When accelerated electrons are direct against an anticathode in an X-ray tube, the radiation obtained has a continuous spectrum with a wavelength minimum,

${\lambda }_{min} =\frac{ (1.24 x {10}^{-6})}{V}$) m, where V is the voltage used for accelerating the electrons.

Calculate $\lambda$_min for V= 5 x 10⁴ volts.

1. 1.25 Å

2. 0.75 Å

3. 0.25 Å

4. 1.00 Å

Calculate the de Broglie wavelength of an $\alpha$-particle emitted from radium having an energy of 4.8 MeV.

(Mass of $\alpha$-particle=6.6 x 10^-24 g; h=Planck's constant = 6.626 x 10^-27 erg sec)

1. 6.18 x 10^-13cm

2. 0.58 x 10^-8cm

3. 6.58 x 10^-13cm

4. 4.12 x 10^-11cm

An atom forms an ion by losing three electrons. The ion has an electronic configuration [Ar]3d⁶. The symbol of the ion is :

When beryllium is bombarded with $\alpha$-particles, extremely penetrating radiations are produced which cannot be deflected by electrical or magnetic fields. These are:

1. Protons

2. $\alpha$ -rays

3. Neutrons

4. X-rays

Using arbitrary energy units we can calculate that 864 arbitrary units (a.u.) are required to transfer an electron in hydrogen atom from the most stable Bohr's orbit to the largest distance from the nucleus 

n = $\infty$   E= 0

n = 1 ;   E= -864 Arbitrary units

The energy required to transfer the electron from third Bohr's orbit to the orbit n = $\infty$will be-

1. 96 Arbitrary units

2. 192 Arbitrary units

3. 288 Arbitrary units

4. 384 Arbitrary units

The sub-shell that comes after f-sub-sell is called g-subshell. The number of g-sub orbitals in g-sub-shell and the total number of orbitals in the principal orbital respectively are-

1. 10 and 25

2. 9 and 25

3. 11 and 23

4. 15 and 45

The wavelengths of two photons are 2000 Å and 4000 Å respectively. What is the ratio of their energies?

1. 1/4

2. 4

3. 1/2

4. 2

Helium atom can be excited to 1s¹, 2p¹ configuration by light of 58.44 nm. The lowest excited state with configuration 1s¹, 2s¹ lies 4857 cm^-1 (1/$\mathrm{\lambda }$) below the 1s¹, 2p¹ state. What would be the average He - H bond energy so that HeH₂ could form, non-endothermically from the lowest excited singlet state of helium? Neglect any difference between $∆$G and $∆$H and take $∆$H as 218 kJ mol^-1

1. 1614 kJ mol^-1

2. 1212 kJ mol^-1

3. 912 kJ mol^-1

4. 1511 kJ mol^-1