Classification of Elements and Compounds

In nature, pure substances exist as either elements or compounds. Depending on the basic unit, elements exist in either atomic or molecular form, while compounds can be subcategorized as either molecular or ionic.

Atomic elements have single atoms as their basic units. Helium, neon, and krypton are examples of monatomic elements that can exist as stable individual atoms.

Molecular elements, on the other hand, contain two or more atoms bonded together, forming a molecule as the basic unit. Diatomic hydrogen with two hydrogen atoms and polyatomic sulfur with eight sulfur atoms are examples of molecular elements.

In comparison to molecular elements, molecular compounds are formed when atoms of two or more nonmetallic elements combine by sharing valence electrons through covalent bonds. 

The combination lowers the overall potential energy of the system, thereby driving the formation of a stable molecule. Hence, the basic units of a molecular compound are discrete molecules composed of constituent atoms.

Ethanol is a molecular compound, which contains basic units of distinct ethanol molecules comprising two carbon, six hydrogen, and one oxygen atoms.

Ionic compounds are formed when atom