Molecule vs. Ion: The Core Difference
The primary difference between a molecule and an ion is their electrical charge. A molecule is an electrically neutral group of two or more atoms held together by chemical bonds, meaning it has an equal number of protons and electrons. An ion, on the other hand, is an atom or group of atoms that has gained or lost one or more electrons, resulting in a net positive or negative electrical charge.
Section 2: Formation and Characteristics
Molecules are formed when atoms share electrons in covalent bonds. They represent the smallest fundamental unit of a chemical compound that can take part in a chemical reaction. In contrast, ions are formed when there is a transfer of electrons. An atom that loses an electron becomes a positively charged cation, while an atom that gains an electron becomes a negatively charged anion.
Section 3: A Practical Example
Consider water (H₂O). A single water molecule is neutral, containing two hydrogen atoms and one oxygen atom sharing electrons. Now, consider table salt (NaCl). In its solid form, it's composed of sodium ions (Na⁺), which have lost an electron, and chloride ions (Cl⁻), which have gained an electron. These oppositely charged ions are attracted to each other, forming an ionic bond.
Section 4: Importance in Chemistry
Understanding this difference is crucial in chemistry. The neutrality of molecules dictates the properties of covalent compounds like sugars and oils. The charge of ions is fundamental to the behavior of ionic compounds, the flow of electricity in solutions (electrolytes), and countless biological processes, such as nerve signal transmission.