In a decay process ${}_{\mathrm{Z}}{}^{\mathrm{A}}\mathrm{X}$ changes into ${}_{\mathrm{Z}-1}{}^{\mathrm{A}}\mathrm{Y}$. Which process is this?

• $\mathrm{\beta }$-decay

• ${\mathrm{\beta }}^{+}$ decay

• $\mathrm{\alpha }$- decay

• $\mathrm{\gamma }$- decay.

Which of the following pairs represent isotones?

• ${}_{33}{}^{77}\mathrm{As},{}_{34}{}^{ 78}\mathrm{Se}$

• ${}_{78}{}^{195}\mathrm{Pt},{}_{76}{}^{190}\mathrm{Os}$

• ${}_{47}{}^{108}\mathrm{Ag},{}_{48}{}^{112}\mathrm{Cd}$

• ${}_{72}{}^{178}\mathrm{Hf},{}_{56}{}^{137}\mathrm{Ba}$

Which of the following arrangement is possible?

• n	l	m	s
  5	2	2	+1/2

• 2

  2

  0

  -1/2

• 3

  -2

  1

  +1/2

• 0

  0

  1

  +1/2

If the mass defect of ${}_4^0\mathrm{X}$ is 0.090 u , then binding energy per nucleon is :

(1 u = 931.5 MeV)

• 9.315 MeV

• 931.5 MeV

• 83.0 MeV

• 8.38 MeV

₂₇Co⁶⁰ is radioactive because :

• its atomic number is high

• it has high $\frac{\mathrm{p}}{\mathrm{n}}$ ratio

• it has high $\frac{\mathrm{n}}{\mathrm{p}}$ ratio

• None of the above

Assertion : For Balmer series of hydrogen spectrum, the value n₁ = 2 and n₂ = 3, 4, 5... .

Reason : The value of n₂ for a line in Balmer series of hydrogen spectrum having the highest wavelength is 6.

• 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.

In nuclear explosion, the energy is released in the form of :

• kinetic energy

• electrical energy

• potential energy

• None of these

The number of atoms in 52 g of He is

• 78.299 x 10²⁴atoms

• 7.820 x 10^-24atoms

• 7.829 x 10²⁴ atoms

• 78.234 x 10²⁵ atoms

89.

Threshold frequency of a metal is 5 $\text{×}$ 10¹³ s^-1 upon which 1 x 10¹⁴s^-1 frequency light is focused. Then the maximum kinetic energy of emitted electron is

• 3.3 $\text{×}$ 10^-21

• 3.3 $\text{×}$ 10^-20

• 6.6 $\text{×}$ 10-²³

• 6.6 $\text{×}$ 10^-20

From elementary molecular orbital theory we can deduce the electronic configuration of the singly positive nitrogen molecular ion as :

• $\mathrm{\sigma }$1s² , $\stackrel{*}{\mathrm{\sigma }}$1s² , $\mathrm{\sigma }$2s² , $\stackrel{*}{\mathrm{\sigma }}$2s² , $\mathrm{\pi }$2p⁴ , $\mathrm{\sigma }$2p¹

• $\mathrm{\sigma }$1s² , $\stackrel{*}{\mathrm{\sigma }}$1s² , $\mathrm{\sigma }$2s² , $\stackrel{*}{\mathrm{\sigma }}$2s² , $\mathrm{\sigma }$2p² , $\mathrm{\pi }$2p³

• $\mathrm{\sigma }$1s² , $\stackrel{*}{\mathrm{\sigma }}$1s² , $\mathrm{\sigma }$2s² , $\stackrel{*}{\mathrm{\sigma }}$2s² , $\mathrm{\sigma }$2p³ , $\mathrm{\pi }$2p²

• $\mathrm{\sigma }$1s² , $\stackrel{*}{\mathrm{\sigma }}$1s² , $\mathrm{\sigma }$2s² , $\stackrel{*}{\mathrm{\sigma }}$2s² , $\mathrm{\sigma }$2p² , $\mathrm{\pi }$2p⁴