A metal surface is exposed to solar radiations :

• the emitted electrons have energy less than a maximum value of energy depending upon frequency of incident radiations

• the emitted electrons have energy less than maximum value of energy depending upon intensity of incident radiations

• the emitted electrons have zero energy

• the emitted electrons have energy equal to energy of photons of incident light

Which of the following transitions have minimum wavelengths ?

• n₄ $\to$ n₁

• n₂ $\to$ n₁

• n₄ $\to$ n₂

• n₃ $\to$ n₁

Orbital is :

• circular path around the nucleus in which the electrons revolves

• space around the nucleus where the probability of finding the electron is maximum

• amplitude of electron wave

• none of the above

634.

Which of the following sequence is correct as per Aufbau principle ?

• 3s < 3d < 4s < 4p

• ls < 2p < 4s < 3d

• 2s < 5s < 4p < 5d

• 2s < 5s < 4p < 5f

A radioactive nucleus will not emit :

• alpha and beta rays simultaneously

• beta and gamma rays simultaneously

• gamma and alpha rays

• gamma rays only

X-rays are emitted during

• $\mathrm{\alpha }$, n reaction

• K-capture

• n, $\mathrm{\alpha }$-reaction

• $\mathrm{\beta }$- emission 

₇₂X¹⁸⁰ $\stackrel{2\mathrm{\alpha }}{\to }$ $\stackrel{\mathrm{\beta }}{\to }$ $\stackrel{\mathrm{\gamma }}{\to }$ _zX^A , Z and A are :

• 69 , 172

• 172 , 69

• 180 , 70

• 182 , 68

Assertion : The quantized energy of an electron is largely determined by its principal quantum number.

Reason : The principal quantum number n is a measure of the most probable distance of finding the electron around the nucleus.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion : C- O bond in metal carbonyl is long.

Reason : There is delocalisation of electrons from filled d orbitals into the empty orbitals on the CO ligands.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false

• If both assertion and reason are false.

Isotopic pair is :

• ₂₀X⁴⁰ , ₂₁X⁴⁰

• ₂₀X⁴⁰ _{, 20}X⁴¹

• ₄₀X²⁰ , ₄₁X²⁰

• None