The atomic numbers of elements X,Y and Z are 19, 21 and 25 respectively. The number of electrons present in the M-shell of these elements follow the order

• Z > X > Y

• X > Y > Z

• Z > Y > X

• Y > Z > X

Which of the following elements has least number of electrons in its M shell ?

• K

• Mn

• Ni

• Sc

An electron is moving in Bohr's fourth orbit. Its de-Broglie wave length is λ. What is the circumference of the fourth orbit ?

• 2/λ

• 2λ

• 4λ

• 4/λ

Which of the following is correct?

• ₁H¹ and ₂He³ are isotopes

• ₆C¹⁴ and ₇N¹⁴ are isotopes

• ₁₉K³⁹ and ₂₀Ca⁴⁰ are isotones

• ₉F¹⁹ and ₁₁Na²⁴ are isodiaphers

What is the correct order of spin only magnetic moment (in BM) of Mn²⁺, Cr²⁺ and V²⁺ ?

• Mn²⁺ > V²⁺ > Cr²⁺

• V²⁺ > Cr²⁺ > Mn²⁺

• Mn²⁺ > Cr²⁺ > V²⁺

• Cr²⁺ > V²⁺ > Mn²⁺ 

The uncertainties in the velocities of two particles A and B are 0.05 and 0.02 m/s^-1 respectively. The mass of B is five times to that of mass A. What is the ratio of uncertainities $\left(\frac{∆{\mathrm{x}}_{\mathrm{A}}}{∆{\mathrm{x}}_{\mathrm{B}}}\right)$ in their positions?

• 2

• 0.25

• 4

• 1

The energy of a photon is 3 × 10^-12 ergs. What is its wavelength in nm ?

(h = 6.62 × 10^-27 ergs ; c = 3 × 10¹⁰ cm/s)

• 662

• 1324

• 66.2

• 6.62

118.

Which of the following is not correct ?

• Nuclei of atoms participate in nuclear reactions

• ₂₀Ca⁴⁰ and ₁₈Ar⁴⁰ are isotones

• 1 amu of mass defect is approximately equal to 931.5 MeV.

• Uranium (U²³⁸) series is known as (4n + 2) series.

An electronic transition in hydrogen atom results in the formation of H_α line of hydrogen in Lyman series, the energies associated with the electron in each of the orbits involved in the transition (in kcal mol^-1) are 

• -313,6, - 34.84

• -313.6, - 78.4

• -78.4,- 34.84

• -78.4,-19.6

The velocities of two particles A and B are 0.05 and 0.02 ms^-1 respectively. The mass of B is five times the mass of A. The ratio of their de-Broglie's wavelength is

• 2 : 1

• 1 : 4

• 1 : 1

• 4 : 1