Ionic and molecular compounds differ primarily in the way they are formed. Ionic compounds form through the transfer of electrons, while molecular compounds form as a result of electron sharing.
Ionic compounds contain atoms and molecules with opposite charges. They bond together as a result of their opposite charges. For instance, a negatively paired ion bonds with a positive ion. Atoms and molecules with like charges repel each other. Molecules with a positive charge are called cations, and molecules with a negative charge are called anions.
Ionic compounds form as a result of atoms or molecules attracting more atoms or molecules with an opposite charge. Composition varies depending on the type of compound, but all ionic compounds must have a neutral electric charge. That means they must have an equal ratio of anionic and cationic molecules.
Ionic compounds are typically solid. They can be made of single atoms, called monatomic compounds, or multiple atoms, which makes them polyatomic compounds. Ionic bonding, which forms ionic molecules, involves the transfer of electrons from metals to non-metals. Metals tend to lose positive electrons readily because they have few electrons in their outer energy level. Non-metals have more negative electrons in their outer energy level. They seek positive ions as a result, and naturally bond with metallic molecules. Most polyatomic compounds are anionic, with the exception of ammonium cation. Ionic compounds differ from molecular compounds in that they can form from metals and non-metals, while molecular compounds can only form from non-metals. Common types of ionic compounds are salt and sugar.
Molecular compounds, also called covalent compounds, share electrons by forming covalent bonds. While ionic compounds can consist of metallic and non-metallic atoms and molecules, covalent bonds can only form from non-metallic atoms and molecules. A covalent compound is formed when atoms within different elements are combined through molecules. This bonding enables the sharing of valence electrons, which creates a common attraction that holds the atoms in the molecule together.
Covalent compounds vary considerably in size. Some are small, with just a few elements, while others can have thousands of atoms. Because they share electrons instead of exchanging them, covalent compounds have considerably different properties than ionic compounds. Covalent compounds tend to burn easily, while ionic compounds do not. In contrast to ionic compounds, they are not water-soluble. Another distinction between the two types of molecules is that covalent compounds cannot conduct electricity, but ionic compounds generally can. At room temperature, most covalent compounds are in liquid or gas form instead of appearing as solids. This is due to the fact that their individual molecules are more easily separated than molecules in a crystal, which gives them a relatively low boiling point. Simple molecular compounds have the same name structure. They are found on the periodic table by naming the element that appears farthest to the left on the table first, then adding "ide" to the second named element and using prefixes to identify the number of atoms in each element. Proteins and carbohydrates are two examples of molecular compounds. Other molecular compounds include methane gas, nitrogen oxide and sodium chloride.