S1.2.1 – The Atomic Model
📌 Atomic model
- An atomic model explains the structure of the atom
- Atomic models change when new evidence is discovered
📌 Dalton’s atomic model
- Atoms are indivisible and solid
- Atoms of the same element are identical
- This model could not explain isotopes or electricity
📌 Rutherford’s nuclear model
- Alpha particles were fired at thin gold foil
- Most particles passed straight through
- Some particles were deflected at large angles
- The atom is mostly empty space
- The nucleus is small, dense, and positively charged
📌 Bohr model
- Electrons occupy fixed energy levels
- Electrons do not lose energy within an energy level
- This model explains the hydrogen emission spectrum
📌 Modern atomic model
- Electrons exist in orbitals, not fixed paths
- Orbitals are regions of probability
- This model is based on quantum mechanics and suggests that each orbital is a region of high probability of finding an electron
- The orbitals are represented by the letters s,p,d and f which correlate to specific energy levels and orbital shapes