Overview
This lecture introduces ionic bonds, explains how ions and compounds form using sodium and chlorine as examples, and briefly discusses the properties of ionic compounds.
Ionic Bonds and Compounds
- An ionic bond occurs when atoms transfer electrons, resulting in oppositely charged ions that attract each other.
- A compound is a substance made of two or more types of atoms bonded together.
- Sodium (Na) has 11 protons and 11 electrons, with a single electron in its third shell.
- Chlorine (Cl) has 17 protons and 17 electrons, with seven electrons in its third shell.
- Atoms tend to achieve full outer electron shells, leading sodium to lose one electron and chlorine to gain one.
Formation of Ions
- When sodium gives its outer electron to chlorine, sodium becomes a positively charged ion (cation), and chlorine becomes a negatively charged ion (anion).
- Ions are atoms that have gained or lost electrons and thus carry an electric charge.
- Oppositely charged ions are attracted to each other, forming an ionic bond.
Properties of Ionic Compounds
- Sodium and chloride ions form sodium chloride (table salt), an example of an ionic compound.
- Ionic bonds are relatively weak; for example, salt dissolves and dissociates into ions when placed in water.
Key Terms & Definitions
- Ionic Bond — a chemical bond formed by the transfer of electrons between atoms, producing oppositely charged ions.
- Compound — a substance containing two or more different elements chemically bonded.
- Ion — an atom with a net electric charge due to the loss or gain of electrons.
- Cation — a positively charged ion (e.g., Na⁺).
- Anion — a negatively charged ion (e.g., Cl⁻).
Action Items / Next Steps
- Review the electron shell structure of sodium and chlorine.
- Prepare to study covalent bonds in the next lecture.