Final Answer:
Ionic compounds almost always contain a metal and at least one type of non-metal atom. Conversely, molecular compounds are composed of only non-metal atoms.
Step-by-step explanation:
Ionic compounds are formed through the transfer of electrons between a metal and a non-metal. Metals, located on the left side of the periodic table, readily lose electrons to achieve a stable electron configuration. Non-metals, on the other hand, gain electrons to complete their outer electron shell. In ionic compounds, the metal atom becomes a positively charged cation, denoted as M^+ , and the non-metal becomes a negatively charged anion, denoted as X^- . For example, sodium chloride (NaCl) consists of Na^+ cations and Cl^- anions. The electrostatic attraction between oppositely charged ions results in the formation of the ionic compound.
In contrast, molecular compounds involve the sharing of electrons between two non-metal atoms. These compounds are formed through covalent bonds, where electrons are shared to achieve a stable electron configuration for both atoms. In molecular compounds, the subscript in the chemical formula represents the number of atoms for each element. For instance, in water (H₂O), there are two hydrogen (H) atoms and one oxygen (O) atom sharing electrons. Molecular compounds typically consist of non-metals only, and their chemical formulas reflect the ratio of atoms in a molecule.
In summary, the presence of a metal and a non-metal indicates an ionic compound, while the absence of a metal signifies a molecular compound, composed solely of non-metal atoms engaged in covalent bonds.