Structure of Atom

An element E loses one $\mathrm{\alpha }$ and two $\mathrm{\beta }$ particles in three successive stages. The resulting elemenl wiil be

• an isobar of E

• an isotone of E

• an isotope of E

• E itself

The electronic transitions from n = 2 to n= 1 will produce shortest wavelength in (where n = principal quantum state)

• Li²⁺ 

• He⁺

• H

• H⁺

What is the wavelength of an α-particle having mass 6.6 × 10^-27 kg moving with a speed of 10⁵ cms^-1? ( h = 6.6 × 10^-34 kgm² - s)?

• 2 × 10^-12 m

• 3 × 10^-10 m

• 1 × 10^-10 m

• 2 × 10^-10 m

Uncertainty principle is valid for

• Proton

• Methane

• Both (a) and (b)

• 1 µm sized platinum particles

The energy of an electron is the 3S orbital ( excited state) of H- atom is

• -1.5 eV

• -13.6 eV

• -3.4 eV

• -4.53 eV

Which transition in the hydrogen atomic spectrum will have the same wavelength as the transition will have the same wavelength, n = 4 to n = 2 of He⁺ spectrum?

• n = 4 to n = 3

• n = 2 to n = 1

• n = 4 to n = 2

• n = 3 to n = 1

The radius of the first Bohr orbit of hydrogen atom is 0.529 Å. The radius of the third orbit of H⁺ will be

• 8.46 Å

• 0.705 Å

• 1.59 Å

• 4.29 Å

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

For a crystal, the angle of diffraction (2 θ) is 90° and the second order line has a d value of 2.28 Å. The wavelength (in Å) of X-rays used for Bragg's diffraction is

• 1.612

• 2.00

• 2.28

• 4.00

The wavelength of a spectral line emitted by hydrogen atom in the Lyman series is $\frac{16}{15\mathrm{R}} \mathrm{cm}$. What is the value of n₂? ( R= Rydberg constant).

• 2

• 3

• 4

• 1