Final answer:
Molecules are formed by combining atoms with chemical bonds, and compounds are created when two or more elements combine in fixed whole number ratios. An empirical formula demonstrates these whole number ratios, as seen in compounds like titanium dioxide with a formula of TiO₂.
Step-by-step explanation:
Molecules are formed when atoms are combined through chemical bonds. The correct answer to what combines to form molecules is Atoms + Chemical bonds = D. Compounds are formed when two or more elements are chemically combined in fixed, whole number ratios. The correct completion for the formation of compounds is Elements + Whole Number Ratios = D.
In chemical reactions, atoms can be combined, separated, or rearranged to form new substances. A compound, such as water (H₂O) or glucose (C₆H₁₂O₆), is a substance composed of two or more elements joined by chemical bonds, which are the result of interactions involving the outermost electrons of the atoms.
An empirical formula represents these compounds by showing the simplest whole-number ratio of the atoms in the compound, such as the TiO₂ in titanium dioxide.