Overview
This lecture explains different types of chemical bonds between atoms—ionic and covalent—and how electrons determine bonding behaviors and molecular structure.
Types of Chemical Bonds
- Atoms bond to other atoms of the same or different elements to form compounds.
- An ionic bond forms when one atom transfers electrons to another, creating oppositely charged ions that attract each other.
- Sodium chloride (table salt) is held together by ionic bonds, forming a 3D lattice.
- A covalent bond forms when atoms share pairs of electrons between them.
- Proteins and DNA are primarily held together by covalent bonds.
Electron Arrangement and Bonding
- Atoms are electrically neutral with equal numbers of protons and electrons.
- Only outermost electrons ("valence electrons") in the highest energy orbitals are involved in bonding.
- In ionic bonding, transferred electrons come from the outermost orbital of the donating atom.
- In covalent bonding, shared electrons also come from the outermost orbitals.
Bonding Capacity of Common Elements
- Carbon has four valence electrons and typically forms four covalent bonds.
- Nitrogen has three valence electrons and typically forms three bonds.
- Oxygen has two valence electrons and usually forms two bonds.
- Hydrogen has one valence electron and forms only one bond.
- Occasionally, atoms can form more bonds than usual under special circumstances.
Molecules and Molecular Size
- Molecules are groups of atoms connected by covalent bonds.
- Molecules can be small, like two oxygen atoms forming O₂, or extremely large, such as human chromosome 13 with billions of atoms.
- Chemical bonds are fundamental in holding atoms together in these structures.
Key Terms & Definitions
- Ionic bond — attraction between oppositely charged ions formed by electron transfer.
- Covalent bond — attraction between atoms that share pairs of electrons.
- Valence electrons — electrons in the outermost orbital involved in bonding.
- Lattice — 3D grid-like arrangement of ions in an ionic compound.
- Molecule — a group of atoms held together by covalent bonds.
Action Items / Next Steps
- Review the definitions and examples of ionic and covalent bonds.
- Practice identifying types of bonds in sample compounds.
- Prepare for a quiz on electron arrangement and bonding capacity of key elements.