An element with atomic mass Z consists of two isotopes of mass number Z-1 and Z + 2. The percentage abundance of the heavier isotope is -

1. 0.25

2. 33.3

3. 66.6

4. 75

Two isotopes of Boron are found in the nature with atomic weights 10.01(I) and 11.01(II). The atomic weight of natural Boron is 10.81. The percentage of (I) and (II) isotopes in it are respectively-

1. 20 and 80

2. 10 and 90

3. 15 and 75

4. 30 and 70

Calculate the wavenumber of lines having the frequency of 5 x 10¹⁶ cycles per sec. 

1. 1.666 x 10⁸m^-1 

2. 0.666 x 10⁸m^-1

3. 4.126 x 10⁶m^-1

4. 3.133 x 10⁴m^-1

Which of the following set of quantum number is not valid

1. n = 1 , $\mathcal{l}$ = 2

2. n=2, m = 1

3. n =3, $\mathcal{l}$ = 0

4. n = 4, $\mathcal{l}$ = 2

For particles having same kinetic energy, the de Broglie wavelength is-

1. Directly proportional to its velocity

2. Inversely proportional to its velocity

3. Independent of velocity and mass

4. Unpredictable

Photochemical dissociation of oxygen results in the production of two oxygen atoms, one in the ground state and one in the excited state.

O₂ $\stackrel{\mathrm{hv}}{\to }$ O→O*

The maximum wavelength () needed for this is 174 nm. If the excitation energy O→O* is 3.15 x 10^-19 J. How much energy in kJ mole^-1 is needed for the dissociation of one mole of oxygen into normal atoms in ground state?

1. 498.3 kJ mol^-1

2. 418.3 kJ mol^-1

3. 524.1 kJ mol^-1

4. 612.8 kJ mol^-1

Rutherford's scattering experiment is related to the size of the-

1. Nucleus

2. Atom

3. Electron

4. Neutron

The  energy needed to convert helium atom  to He ⁺² is -79eV. The first ionization energy of this atom is about 

1. 65.4eV

2. 51.8eV

3. 24.6eV

4. 27.2eV

Elements upto atomic number 103 have been synthesized and studied. If a newly discovered element is found to have an atomic number 106, its electronic configuration will be -

1. [Rn] 5f¹⁴, 6d⁴, 7s²

2. [Rn] 5f¹⁴, 6d¹, 7s² 7p³

3. [Rn] 5f¹⁴, 6d, 7s⁰

4. [Rn] 5f¹⁴, 6d⁵, 7s¹

The most probable radius (in pm) for finding the electron in He⁺ is -

1. 0

2. 52.9

3. 26.5

4. 105.8