Overview
This lecture explains the fundamental structure of atoms and molecules, describing their components, electron arrangement, and chemical bonding.
Structure of Atoms
- Atoms are the basic building blocks of all matter.
- Atoms consist of protons, neutrons, and electrons.
- Protons (positive charge) and neutrons (no charge) are in the nucleus, making it positively charged.
- Electrons (negative charge) orbit the nucleus in defined paths called shells or orbits.
- Atoms are electrically neutral because they have equal numbers of protons and electrons.
Electron Arrangement
- Electrons revolve in specific orbits (shells) named K, L, M, etc.
- The maximum electrons in a shell is given by the formula 2n², where n is the orbit number.
- The K shell holds 2, L shell 8, and M shell 18 electrons.
- Electrons in the outermost shell are called valence electrons; this shell is the valence shell.
Molecules and Chemical Bonding
- Molecules are groups of two or more atoms chemically bonded together.
- Atoms combine to form molecules by gaining or losing valence electrons, often under external influences like heat or light.
- Chemical bonds joining atoms are mainly covalent (sharing electrons) or ionic (transferring electrons).
- Molecules with atoms of the same element are called homoatomic; those with different elements are heteroatomic.
Key Terms & Definitions
- Atom — the smallest unit of matter, made of protons, neutrons, and electrons.
- Proton — positively charged particle in the nucleus.
- Neutron — neutral particle in the nucleus.
- Electron — negatively charged particle orbiting the nucleus.
- Shell/Orbit — path around nucleus where electrons are found.
- Valence Electrons — electrons in the outermost shell.
- Molecule — group of two or more atoms chemically bonded.
- Covalent Bond — bond formed by sharing electrons.
- Ionic Bond — bond formed by transferring electrons.
- Homoatomic Molecule — molecule with atoms of the same element.
- Heteroatomic Molecule — molecule with atoms of different elements.
Action Items / Next Steps
- Review the structure and components of atoms and molecules.
- Practice calculating maximum electrons in shells using 2n² formula.