The element with atomic number $12$ belongs to ......... group and ......... period.

The existence of a substance in more than one solid modification is known as:

The instantaneous angular position of a point on a rotating wheel is given by the equation $\theta(t) = 2t^3 - 6t^2$. The torque on the wheel becomes zero at $t = $ ....... $\text{sec}$.

If the circle $x^2+y^2+6x-2y+k=0$ bisects the circumference of the circle $x^2+y^2+2x-6y-15=0$,then $k=$

The spin magnetic moment of cobalt in the compound $Hg[Co(SCN)_4]$ is