1. 3.4 Models of the Atom

2. Niels Bohr Niels Bohr, a Danish Physicist developed the “ planetary ” model of the atom. Electrons travel around the nucleus in orbits, much like the planets travel around the Sun. He Electron Nucleus Orbit

3. Things to know: Order of filling the electrons is 2 in the first orbit, maximum of 8 in the second orbit, and maximum of 8 in the third… (2,8,8) Electrons are more stable closer to the nucleus. The further away the electrons are from the nucleus, the greater the energy they have. Electrons can move from one orbit to another, but they don ’ t exist in between. Heat, light, or electricity can allow electrons to jump from one orbit to another.

4. Bohr Diagrams Symbol is in the centre (nucleus) and the electrons orbit around it: Ex. Hydrogen Ex. Nitrogen Ex. Phosphorus

5. Hydrogen H 1 e- Chemical Symbol in the center

6. Nitrogen N 7 e-

7. Phosphorus P 15 e-

8. Bohr-Rutherford Rutherford developed the “ nuclear ” model of the atom and when combined with Bohr ’ s diagram, we can see the numbers and position of all 3 subatomic particles: protons, neutrons, electrons.

9. Bohr-Rutherford The number of protons and neutrons are written in the centre (nucleus) and the electrons are still represented on the orbits: Ex. Phosphorus Atomic Mass - 31 Atomic # 15 (P=15, e-=15) (*Neutrons = At Mass – At #) Complete p 93: 4-5

10. Page 93: 4 Oxygen Aluminum Calcium

11. Page 93: 5 Flourine Boron Potassium

12. http://www.chemicalelements.com/ 1

13. Chapter 3 Review Questions 2,3,5,7,10,11,12 and 13 pages 100 and 101