The number of unpaired electrons in 1s² 2s² 2p³ is -

1. 2

2. 0

3. 3

4. 1

The wavelength of a certain line in the Balmer series is observed to be 4341 A^o for hydrogen atoms.
The electronic transition among the following may be:

1. 3 → 2
2. 4 → 1
3. 5 → 2
4. 5 → 3

A photon with an initial frequency of \(10^{11}~\mathrm{Hz}\) scatters off an electron at rest. Its final frequency is \(0.9 \times10^{11}~\mathrm{Hz}.\) The speed of scattered electron is close to: 

Photons of wavelength 4000 $A^o$ are used to break ${\mathrm{l}}_2$ molecules. The percentage of energy converted
to the kinetic energy of atoms will be:

[Given: Bond dissociation energy of the molecule is 246.5 kJ/mol]

1.  12%

2.  8%

3.  26%

4.  17%

The number of protons, neutrons and electrons in  \( _{71}^{175}Lu\) respectively, are:

1. 104, 71 and 71

2. 71, 71 and 104

3. 175, 104 and 71

4. 71, 104 and 71

The energy of an electron in the first Bohr's orbit of an H-atom is -13.6 eV. The possible energy value (s) of the excited state(s) for electrons in Bohr's orbits of hydrogen is (are):

1. -3.4 eV

2. -4.2 eV

3. -6.8 eV

4. +6.8 eV

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. ${\mathrm{Li}}^{2+},\mathrm{n}=3$

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

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