Give reasons: Diamond is used as an abrasive.

What are the ions called that possess properties similar to halide ions and consist of two or more electronegative atoms,at least one of which is nitrogen?

Evaluate the following statements related to group $14$ elements for their correctness.
$(A)$ Covalent radius decreases down the group from $C$ to $Pb$ in a regular manner.
$(B)$ Electronegativity decreases from $C$ to $Pb$ down the group gradually.
$(C)$ Maximum covalence of $C$ is $4$ whereas other elements can expand their covalence due to presence of $d$ orbitals.
$(D)$ Heavier elements do not form $p\pi-p\pi$ bonds.
$(E)$ Carbon can exhibit negative oxidation states.
Choose the correct answer from the options given below:

The presence of $Si$ in steel gives it

Which of the following statements is correct with respect to the property of elements with an increase in atomic number in the carbon family (group $14$)?

The stability of dihalides of $Si, Ge, Sn$ and $Pb$ increases in the order: