1. Models of the Atom
SCH4C September 2017

2. Democritus 400 BC
Atom = indivisible = smallest unit of matter

3. John Dalton 1800

4. J. J. Thomson 1897

5. 1897
Thomson discovers that atoms contain negatively charged particles called
electrons

6. Thomson’s Model of the Atom

7. Nagaoka’s Model 1904

8. Ernest Rutherford 1911

9. 1918
Rutherford discovers that atoms contain positively charged particles called
protons

11. Neils Bohr 1922

14. Recall from grade 10: Light travels in waves – some we see, some we can’t

15. Each wavelength we see as a unique colour Each wavelength has a different amount of energy

16. White Light: when passed through a prism we see every colour of light possible (continuous spectrum)

17. Bohr’s Model: Electrons exists in orbits called energy levels
Bohr’s Model: Electrons exists in orbits called energy levels. Energy levels are labelled as n=1 (the first energy level), n = 2 etc.

18. Bohr proposed that:
When atoms were given energy (heated up or has electricity pass through them) the electrons gained energy and moved up to higher energy levels (excited state)
When electrons returned to their original energy level (ground state), they released energy

20. We see the energy released as different colours
We see the energy released as different colours. This is unique for each element and therefore a good way to identify an element.

21. Spectra produced by different elements (line spectra)