Overview
This lecture explains ionic bonds, detailing how they form between metals and nonmetals through electron transfer, and uses sodium chloride as a primary example.
Ionic Bonds: Definition and Basics
- Ionic bonds form between a metal and a nonmetal.
- In ionic bonding, one atom gives up electrons and another atom takes them, resulting in charged atoms (ions).
- These bonds are stable when dry but easily fall apart in water.
- Table salt (sodium chloride, NaCl) is a classic example of an ionic bond.
Electron Configuration and Ion Formation
- The number of electrons in a neutral atom equals the number of protons (atomic number).
- Sodium (Na) has one valence electron after filling inner shells (11 total electrons: 2 in first shell, 8 in second, 1 in outer).
- Chlorine (Cl) has seven valence electrons (17 total electrons: 2 in first shell, 8 in second, 7 in outer).
- Sodium easily loses its one valence electron to achieve a full outer shell.
- Chlorine needs to gain one electron to complete its valence shell.
Charges and Attraction in Ionic Bonds
- When sodium gives up its electron, it becomes a positively charged ion (Na⁺).
- When chlorine gains an electron, it becomes a negatively charged ion (Cl⁻).
- The electrostatic attraction between these oppositely charged ions forms the ionic bond.
- Ionic compounds dissolve in water due to polarity: water molecules attract the charged ions.
Key Terms & Definitions
- Ionic Bond — a chemical bond formed by the transfer of electrons from one atom (metal) to another (nonmetal), resulting in oppositely charged ions.
- Ion — a charged atom or molecule (positive: cation, negative: anion).
- Valence Electrons — electrons in the outermost shell that determine an atom's bonding behavior.
- Electrostatic Attraction — the force holding oppositely charged ions together in an ionic bond.
Action Items / Next Steps
- Practice drawing electron configurations and predicting the charges for other ionic compounds.
- Prepare more examples of ionic bonds (e.g., potassium chloride) for class discussion.