A thorium nucleus is formed when a uranium nucleus emits an $\mathrm{\alpha } - \mathrm{particle}$. The atomic number of thorium is

1.  92

2.  90

3.  82

4.  94

The activity of the radioactive element decreases to one-third of the original activity ${\mathrm{A}}_0$ in a period of 7 years. After a further lapse of 7 years, its activity will be:

1.  ${\mathrm{A}}_0$ $$ $$

2.  $\frac{2}{3}{\mathrm{A}}_0$ $$ $$

3.  $\frac{{\mathrm{A}}_0}{6}$ $$ $$

4.  $\frac{{\mathrm{A}}_0}{9}$

The radius of Germanium (Ge) nuclide is measured to be twice the radius of ${}_4{}^9\mathrm{Be}$. The number of nucleons in Ge is:

1. 73

2. 74

3. 75

4. 72

A radioactive nucleus X decays to a stable nucleus 'y'. The graph of the rate of formation of 'y' against time 't' will be:

1.		2.
3.		4.

A stationary radioactivity nucleus of mass 210 units disintegrates into an alpha particle of mass 4 units and residual nucleus of mass 206 units. If the kinetic energy of the alpha particles is E, the kinetic energy of the residual nucleus is 

1.  $\left(\frac{2}{105}\right) \mathrm{E}$

2.  $\left(\frac{2}{103}\right) \mathrm{E}$

3.  $\left(\frac{103}{105}\right) \mathrm{E}$

4.  $\left(\frac{103}{2}\right) \mathrm{E}$

The mass number of a nucleus is

1.  sometimes equal to its atomic number

2.  sometimes less than and sometimes more than its atomic number

3.  always less than its atomic number

4.  always more than its atomic number

$\mathrm{Two} \mathrm{nucleons} \mathrm{are} \mathrm{at} \mathrm{a} \mathrm{separation} \mathrm{of} 1 \mathrm{fm}. \mathrm{The} \mathrm{net} \mathrm{force} \mathrm{between} \mathrm{them} \mathrm{is} {\mathrm{F}}_1 \mathrm{if} \mathrm{both} \mathrm{are} \mathrm{neutrons}, {\mathrm{F}}_2 \mathrm{if} \mathrm{both} \mathrm{are} \mathrm{protons} \mathrm{and} {\mathrm{F}}_3 \mathrm{if} \mathrm{one} \mathrm{is}$
$\mathrm{proton} \mathrm{and} \mathrm{other} \mathrm{is} \mathrm{a} \mathrm{neutron}. \mathrm{Hence}$

1.  ${\mathrm{F}}_1 > {\mathrm{F}}_2 > {\mathrm{F}}_3$

2.  ${\mathrm{F}}_2 > {\mathrm{F}}_1 > {\mathrm{F}}_3$

3.  ${\mathrm{F}}_1 = {\mathrm{F}}_3 > {\mathrm{F}}_2$

4.  ${\mathrm{F}}_1 = {\mathrm{F}}_2 > {\mathrm{F}}_3$

$In the nucleus of {}_{11}{}^{23}Na, \mathrm{the} \mathrm{number} \mathrm{of} \mathrm{protons}, \mathrm{neutrons} \mathrm{and} \mathrm{electrons} \mathrm{are}$:

1.  11, 12, 0

2.  23, 12, 11

3.  12, 11, 0

4.  23, 11, 12

In the nuclear decay given below

${}_{\mathrm{z}}{}^{\mathrm{A}}\mathrm{X} \stackrel{}{\to } {}_{\mathrm{Z} + 1}{}^{\mathrm{A}}\mathrm{Y} \stackrel{}{\to } {}_{\mathrm{Z} - 1}{}^{\mathrm{A} - 4}\mathrm{B}_{*} \stackrel{}{\to } {}_{\mathrm{Z} - 1}{}^{\mathrm{A} - 4}\mathrm{B},$

$\mathrm{The} \mathrm{particles} \mathrm{emitted} \mathrm{in} \mathrm{the} \mathrm{sequence} \mathrm{are}$
$$

1.  $\mathrm{\beta }, \mathrm{\alpha }, \mathrm{\gamma }$

2.  $\mathrm{\gamma }, \mathrm{\beta }, \mathrm{\alpha }$

3.  $\mathrm{\beta }, \mathrm{\gamma }, \mathrm{\alpha }$

4.  $\mathrm{\alpha }, \mathrm{\beta }, \mathrm{\gamma }$