The isoelectronic pair is

• Cl₂O, ICl₂^-

• ICl₂^-, ClO₂

• IF₂⁺, I₃^-

• ClO₂^-, ClF₂⁺

α-Particles can be detected using

• thin aluminium sheet

• barium sulphate

• zinc sulphide screen

• gold foil

393.

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

• 0.0

• 52.9

• 26.5

• 105.8

How many neutrons are there in nucleus 'X', if it gives ₇N¹⁴ after two successive $\mathrm{\beta }$ - particle emissions ?

• 7

• 10

• 14

• 09

The energy equivalent to 1 amu., is :

• 931.1 MeV

• 1.492 x 10¹³ erg

• 1000 J

• 10⁷ erg

Which particle can be used to change ₁₃Al²⁷ into ₁₅P³⁰ ?

• Neutron

• $\mathrm{\alpha }$ - particle

• Proton

• Deuteron

According to Bohr, the angular momentum of an electron, in any orbit, should be :

• h/2$\mathrm{\pi }$

• nh/2$\mathrm{\pi }$

• h/mv

• 2$\mathrm{\pi }$/nh

Quantum numbers of an atom can be defined on the basis of :

• Hund's rule

• Pauli's exclusion principle

• Aufbau's principle

• Heisenberg's uncertainty principle

Which of the following has maximum energy ?

• 
  3s                      3p                                     3d

  $⥮$

  $⥮$

  $\uparrow$

  $\uparrow$

• 3s                      3p                                   3d

  $⥮$

  $\uparrow$

  $\uparrow$

  $\uparrow$

  $\uparrow$

• 3s                     3p                                     3d

  $⥮$

  $\uparrow$

  $\uparrow$

  $\uparrow$

  $\uparrow$

  $\uparrow$

• 3s                    3p                                 3d

  $⥮$

  $\uparrow$

  $\uparrow$

  $\uparrow$

  $\uparrow$

Spectrum of Li²⁺ is similar to that of :

• H

• Be

• He

• Ne