Molecules and compounds often get used interchangeably, but there is a distinct difference between them. Both molecules and compounds are combinations of two or more atoms, but the distinction is how those atoms are combined. Molecules are combinations of atoms that can be broken apart, while compounds are combinations of atoms that can’t be broken by normal means.

Atoms and Chemical Bonds

Atoms are the smallest particles that make up matter, and they’re made up of protons, neutrons and electrons. When two atoms come together, they form a chemical bond or a connection. Chemical bonds are formed when electrons are shared between atoms.

Atoms can become molecules when they share electrons and form chemical bonds. Molecules have different shapes depending on the type of electrons shared, and the bond formed. For example, when two oxygen atoms come together, they form a molecule with a bent shape because they share a double bond.

Compound Formation

Compounds differ from molecules in that they involve the sharing of two or more pairs of electrons, instead of just one pair. In many cases, the atoms that are involved in the compound are from different elements. An example of a compound is table salt, also known as sodium chloride. In this case, one sodium atom is combined with one chlorine atom.

Compounds are held together more strongly than molecules. This happens because more electrons are shared, creating a stronger bond. These bonds are harder to break than molecules, and normal chemical processes cannot break them.

Stoichiometry and Chemical Reactions

Molecules and compounds can also be used to represent chemical reactions. This concept is called stoichiometry, and it seeks to illustrate the amount of reactants and products in a chemical reaction. In this case, molecules and compounds are represented by chemical formulas or equations. The formulas provide information about the elements involved in the chemical reaction, as well as the ratio of reactants and products.

For example, the equation for the combustion of ethane looks like this: C2H6 + O2 -> CO2 + H2O. The equation shows that two molecules of ethane, represented as C2H6, react with one molecule of oxygen, represented as O2, to produce one molecule of carbon dioxide and one molecule of water.

Differences in Properties

The difference between molecules and compounds goes beyond their formation. Molecules tend to have properties that are different from compounds; molecules are usually gases or liquids at room temperature, while compounds are usually solids. They can also be distinguished by their boiling and melting points, as they usually have different ones.

Molecules and compounds also differ in terms of their reactivity. Molecules tend to be more reactive than compounds because their bonds are weaker. Compounds are less likely to react because of their stronger bonds.

Molecule and Compound Naming

Another way to differentiate between molecules and compounds is to look at how they are named. Molecules often use Greek prefixes to indicate how many of each atom are present. For example, the molecule water is named H2O, because it contains two hydrogen atoms and one oxygen atom.

Compounds, on the other hand, use the names of the elements involved. For example, table salt is named sodium chloride, because it contains one atom of sodium and one atom of chlorine. These names often contain the suffix “ide” to indicate they are compounds, such as in the case of sodium chloride.

Molecule and Compound States

In terms of their states of matter, molecules and compounds can behave in different ways. Molecules may be found in liquid or gaseous states at room temperature, while compounds are usually solids at room temperature. Molecules and compounds can also exist in different forms, depending on their bonding.

For example, carbon dioxide can exist as a solid, a liquid, or a gas depending on its temperature. By contrast, table salt only exists as a solid at room temperature because of its stronger bonds.

Solubility

The difference between molecules and compounds can also be seen when it comes to solubility. Molecules are typically more soluble in water than compounds are. This is because molecules tend to be polar, meaning that one side of the molecule is positively charged and the other is negatively charged. This makes the molecule attract to water molecules, allowing it to dissolve.

Compounds, on the other hand, are usually non-polar and don’t attract to water molecules as easily. As a result, they’re usually not as soluble in water as molecules are.

Differences in Weight

The molecular weight of molecules and compounds can also be used to distinguish between them. Molecular weight is the sum of the mass of all the atoms in a molecule or compound. Molecules tend to have lower molecular weights than compounds, because compounds are made up of more atoms than molecules.

For example, table salt has a molecular weight of 58.44 g/mol, which is much greater than the molecular weights of water (18.015 g/mol) or carbon dioxide (44.01 g/mol).

Summary

Molecules and compounds may seem like similar terms, but there is an important difference between them. Molecules are combinations of two or more atoms that are held together by one pair of electrons, while compounds are combinations of two or more atoms that are held together by two or more pairs of electrons. In terms of their properties, molecules and compounds can differ in their reactivity, solubility, weight and states of matter.

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