1. Other Discoveries Other Discoveries Electron Charge (-1) Electron Charge (-1) Protons Protons Mass is 1836 times an electron Mass is 1836 times an electron Charge is (+1) Charge is (+1) Neutrons Neutrons James Chadwick, 1932 James Chadwick, 1932 No Charge No Charge

2. Bohr Model of the Atom How are electrons arranged around the nucleus so that they do not fall in? How are electrons arranged around the nucleus so that they do not fall in? Planetary Model Planetary Model Electrons are in circular “orbits” around nucleus Electrons are in circular “orbits” around nucleus Would eventually collapse Would eventually collapse + + + + + + o o o o o o o o e-e-e-e- e-e-e-e- e-e-e-e- e-e-e-e- e-e-e-e- e-e-e-e-

3. In Proportion If the nucleus was the size of a pen point If the nucleus was the size of a pen point The first electron would be 137 m away The first electron would be 137 m away

4. Bohr Model of the Atom How are electrons arranged around the nucleus so that they do not fall in? How are electrons arranged around the nucleus so that they do not fall in? Planetary Model Planetary Model Electrons are in circular “orbits” around nucleus Electrons are in circular “orbits” around nucleus Would eventually collapse Would eventually collapse + + + + + + o o o o o o o o e-e-e-e- e-e-e-e- e-e-e-e- e-e-e-e- e-e-e-e- e-e-e-e-

5. Atomic Components Electron (e - ) Electron (e - ) Negative charge (-1) Negative charge (-1) Found outside nucleus Found outside nucleus Very tiny (9.110 x 10 -28 g or 0.000549 AMU) Very tiny (9.110 x 10 -28 g or 0.000549 AMU) Proton (p + ) Proton (p + ) Positive charge (+1) Positive charge (+1) Found in nucleus Found in nucleus Much larger (1.673 x 10 -24 g or 1.0073 AMU) Much larger (1.673 x 10 -24 g or 1.0073 AMU) Neutron (n o ) Neutron (n o ) Neutral charge Neutral charge Found in nucleus Found in nucleus Slightly larger than a proton (1.675 x 10 -24 g or 1.0087 AMU) Slightly larger than a proton (1.675 x 10 -24 g or 1.0087 AMU) Atomic Mass Units

6. Isotopes Atomic Number Atomic Number Number of protons Number of protons Gives identity (always the same) Gives identity (always the same) Mass Number Mass Number Number of protons and neutrons Number of protons and neutrons May vary for the same atom type May vary for the same atom type Isotopes – atoms with the same number of protons and a different number of neutrons Isotopes – atoms with the same number of protons and a different number of neutrons Neon-20 Neon-20 Neon-21 Neon-21 Neon-22 Neon-22 10 p + 10 n o 10 p + 11 n o 10 p + 12 n o Mass Number

7. Number of p + = number of e - (neutral) Number of p + = number of e - (neutral) Carbon-12 Carbon-12 Carbon-14 Carbon-14 6 p + 6 e - 6n o 6 p + 6 e - 8n o (Radioactive) Symbol Mass Number Atomic Number

8. Practice: Practice: 82: 29a. 94 Pu b. 95 Am c. 89 Ac d. 55 Cs e. 77 Ir f. 25 Mn 241 244 227 133 56 193 94 p + 95 p + 89 p + 55 p + 77 p + 25 p + 150 n 0 89 e - 95 e - 55 e - 77 e - 25 e - 94 e - 146 n 0 138 n 0 78 n 0 116 n 0 31 n 0

9. 28: 30 NameSymbol Atomic Number Mass Number Neutrons Sodium-231123 Nitrogen-15 7N7N7N7N 56 Ba Lithium-96 Boron-11511 15 136