Which of the following metals exist in their native state in nature?
$(i)$ $Cu$
$(ii)$ $Au$
$(iii)$ $Zn$
$(iv)$ $Ag$

Which of the following gases is combustible?

Which of the following pairs will give displacement reactions?

What type of oxides are formed when non-metal elements combine with dioxygen gas?

An element $A$ burns with a golden yellow flame in air. It reacts with another element $B$ (atomic number $17$) to give a product $C$. An aqueous solution of product $C$ on electrolysis gives a compound $D$ and liberates hydrogen. Identify $A$,$B$,$C$,and $D$. Also,write down the equations for the reactions involved.

$A$ compound $Z$ is formed by the transfer of electrons from a metal $X$ to a non-metal $Y$. Identify the type of bond formed in the compound. List three general properties of the compounds formed by such type of bonds.