Topic 1: The Atom

Dalton’s Model

Elements are made of Atoms; Atoms of an element are the same; Compounds are formed from combinations of atoms.

Rutherford Experiment

Demonstrated that atoms are mostly empty space with a small, dense positively charged nucleus.

Bohr Model

Describes a small, dense, positively charged nucleus surrounded by electrons in circular orbits.

Wave Mechanical Model

Consists of a small dense nucleus surrounded by electrons in an electron cloud, with orbitals representing areas where an electron is likely to be found.

Number of Protons and Electrons

The number of protons in an atom is equal to the number of electrons.

Energy Levels and Orbitals

Electrons fill energy levels and orbitals starting from the one requiring least energy. Valence electrons require the most energy.

Excited State of Electron

When an electron gains energy, it moves to a higher orbital and enters the 'excited state.'

Photon Emission

When an electron returns to a lower energy state, it emits energy, typically in the form of light.