An element $(X)$ forms compounds of the formula $XCl_3$,$X_2O_5$ and $Ca_3X_2$,but does not form $XCl_5$. Which of the following is the element $X$?

The greatest threat to genetic diversity in agricultural crops is

The oxide of a metal contains $40 \%$ of oxygen. The valency of the metal is $2$. What is the atomic weight of the metal?

The major product of the following reaction is

For a telescope,the focal length of the objective lens is $15 \ cm$ and the focal length of the eyepiece is $10 \ mm$. If the tube length is $16 \ cm$,find the magnification.

The orbital angular momentum of a $3p$ electron is