If the bindings energy of the electron in a hydrogen atom is 13.6 eV, the energy required to remove the electron from the first excited state of Li⁺⁺ is

• 30.6 eV

• 13.6 eV

• 3.4 eV

• 6.8 eV

302.

The fraction of atoms of radioactive element that decays in 6 days is 7 / 8. The fraction that decays in 10 days will be

• 77 / 80

• 71 / 80

• 31 / 32 

• 15 / 16

In β⁺ decay process, which of the following changes takes place inside the nucleus

• ${}_{\mathrm{Z}}{}^{\mathrm{A}}\mathrm{X} \to {}_{\mathrm{Z}+1}{}^{\mathrm{A}}\mathrm{Y} + {\mathrm{e}}^{+} + \mathrm{v}$

• ${}_{\mathrm{Z}}{}^{\mathrm{A}}\mathrm{X} \to {}_{\mathrm{Z}+1}{}^{\mathrm{A}}\mathrm{Y} + {\mathrm{e}}^{-} + \stackrel{-}{\mathrm{v}}$

• ${}_{\mathrm{Z}}{}^{\mathrm{A}}\mathrm{X} \to {}_{\mathrm{Z}}{}^{\mathrm{A}}\mathrm{Y} + {\mathrm{e}}^{-} + \mathrm{v}$

• ${}_{\mathrm{Z}}{}^{\mathrm{A}}\mathrm{X} \to {}_{\mathrm{Z}}{}^{\mathrm{A}}\mathrm{Y} + {\mathrm{e}}^{-} + \stackrel{-}{\mathrm{v}}$

The fossil bone has a ¹⁴C : ¹²C ratio which is (1 / 16) of that in a living animal bone. If the half-life time of ¹⁴C is 5730 years, thus the age of the fossil bone is

• 11460 years

• 17190 years

• 22920 years

• 45840 years

If M is atomic mass, A is mass number of a nucleus, then $\frac{\mathrm{M} - \mathrm{A}}{\mathrm{A}}$ is called

• mass defect

• fermi energy

• binding energy

• packing fraction

The half-life of a radio-isotope is 4 h. If initial mass of the isotope was 200 g, then mass remaining after 24 h will be

• 1.042 g

• 2.084 g

• 3.125 g

• 4.167 g

A radioactive nucleus A finally transforms into a stable nucleus B. Then A and B can be

• isobars

• isotones

• isotopes

• none of these

If ₉₂U²³⁸ emits 8 $\mathrm{\alpha }$-particles and 6 β-particles, then the resulting nucleus is

• ₈₂U²⁰⁶

• ₈₂Pb²⁰⁶

• ₈₂U²¹⁰

• ₈₂U²¹⁴

C¹⁴ has half-life 5700 yr. At the end of 11400 yr, the actual amount left is

• 0.5 of original amount

• 0.25 of original amount

• 0.125 of original amount

• 0.0625 of original amount

Li nucleus has three protons and four neutrons. Mass of lithium nucleus is 7.016005 amu. Mass of proton is 1.007277 amu and mass of neutron is 1.008665 amu. Mass defect for lithium nucleus in amu is

• 0.04048 amu

• 0.04050 amu

• 0.04052 amu

• 0.04055 amu