Final answer:
Ammonia (NH3) is an example of a binary compound because it consists of two different elements, nitrogen and hydrogen. Option 4 is correct.
Step-by-step explanation:
An example of a binary compound is ammonia (NH3). A binary compound is one made up of two different elements. In the options provided, mercury is an element, ethanol is an organic compound containing carbon (C2H5OH), and sodium is again an element. The correct answer, ammonia, consists of nitrogen (N) and hydrogen (H), with the chemical formula NH3, making it a compound composed of two different elements.
A binary compound is a compound composed of two different elements. In the given options, ammonia (NH3) is the only example of a binary compound. Ammonia is composed of two elements, nitrogen and hydrogen. It is a covalent compound, as it is composed of nonmetal elements bonding through covalent bonds.