Overview
This lecture covers how to calculate the maximum number of electrons in electron shells, defines atomic orbitals and subshells, and describes the shapes of s and p orbitals.
Electron Shells and Quantum Numbers
- Electrons exist in electron shells, also called main energy levels.
- Each shell has a principal quantum number (n): shell 1 = n=1, shell 2 = n=2, etc.
- Maximum electrons per shell: 2n² (where n is the principal quantum number).
- Shell capacities: 1st = 2, 2nd = 8, 3rd = 18, 4th = 32 electrons.
- Higher-numbered shells have more energy and hold more electrons.
Atomic Orbitals
- Atomic orbital: region around the nucleus that can hold up to two electrons with opposite spins.
- Electrons in the same orbital must have opposite spins (up and down).
- Electrons are considered as negative charge clouds shaped like orbitals.
- The orbital defines a 95% probability of finding an electron in a region.
Types and Shapes of Orbitals
- Four types of orbitals: s, p, d, and f.
- S orbital: spherical shape; each shell has one s orbital.
- P orbitals: dumbbell-shaped; each shell except the first has three p orbitals.
- D orbitals: complex shapes; shells 3 and above have five d orbitals (shape details not required).
- F orbitals: seven per shell; only in shells 4 and above.
Subshells
- Subshell: all orbitals of the same type within a shell (e.g., 2p subshell = all p orbitals in shell 2).
- AQA may refer to subshells as sub levels.
Key Terms & Definitions
- Electron Shell (Main Energy Level) — region around the nucleus where electrons are found, labeled by principal quantum number (n).
- Principal Quantum Number (n) — number indicating the shell’s energy level.
- Atomic Orbital — region where up to two electrons with opposite spins are likely to be found.
- Spin — property of electrons; two electrons in an orbital must have opposite spins.
- Subshell — group of the same type of orbitals in one shell (e.g., s, p, d, f).
- S orbital — spherical orbital; one per shell.
- P orbital — dumbbell-shaped; three per shell (except shell 1).
Action Items / Next Steps
- Review how electrons are assigned to atomic orbitals in the next video.
- Note AQA differences: "main energy levels" for shells, "sub levels" for subshells.