The correct order of $C-O$ bond length in $CO$,$CO_3^{2-}$ and $CO_2$ is:

Which one of the following reactions does not form a gaseous product?

Select the correct option on the basis of the following sentences regarding a gland's function:
$(I)$ Hormones increase alertness.
$(II)$ Hormones increase the heart beat.
$(III)$ Stimulate the breakdown of glycogen.
$(IV)$ Stimulate the breakdown of lipids and proteins.

The half-life of a radioactive isotope $X$ is $50 \, years$. It decays to another element $Y$ which is stable. The two elements $X$ and $Y$ were found to be in the ratio of $1 : 15$ in a sample of a given rock. The age of the rock was estimated to be ........ $years$.

What is the total number of orbitals associated with the principal quantum number $n=3$?

In the isoelectronic series of metal carbonyls,the $CO$ bond strength is expected to increase in the order: