In the nuclear reaction,${ }_{90}^{234} Th \longrightarrow{ }_{91}^{234} Pa + X$,$X$ is:

Which of the following pairs of transition metal ions have the same calculated values of magnetic moment?

From which of the following minerals is $Ra$ (Radium) obtained?

From the following statements,select the wrong one:

If the harmonic mean of the roots of the equation $\sqrt{2}x^2 - bx + (8 - 2\sqrt{5}) = 0$ is $4$,then the value of $b$ is:

Heat energy is incident on the surface at the rate of $1000 ~J/min$. If the coefficient of absorption is $0.8$ and the coefficient of reflection is $0.1$,then the heat energy transmitted by the surface in $5 ~min$ is: (in $~J$)