1. Atomic Theory Modern Model

2. atom (page 313) smallest part of an element that has all the properties of the element.

3. Two parts nucleus (page 316) – tiny, extremely dense, positively charged, center of the atom electron cloud (page 317) – regions where electrons are likely to be found

4. The atom is mostly empty space. See Figure 7 on page 316.

5. Subatomic particles ParticleSymbolLocationCharge protonp+p+ neutronnono electrone-e-

6. ParticleSymbolLocationCharge protonp+p+ nucleus neutronnono nucleus electrone-e- electron cloud

7. ParticleSymbolLocationCharge protonp+p+ nucleus1+ neutronnono nucleusnone (0) electrone-e- electron cloud 1-

8. atomic number Number of protons = number of electrons Identifies the element. Locate on the periodic table. (Page 768-769)

9. Study Buddies 1)How many protons does carbon have? 2)How many electrons does carbon have? 3)How many protons does chlorine have? 4) How many electrons does aluminum have? 5)What element has 20 protons? 6)What element has 16 electrons?

10. Answers 1)How many protons does carbon have? (6) 2)How many electrons does carbon have? (6) 3)How many protons does chlorine have? (17) 4)How many electrons does aluminum have? (13) 5)What element has 20 protons? (calcium) 6)What element has 16 electrons? (sulfur)

11. Atomic Theory Model These energy levels or shells follow a very predictable pattern. The closest shell to the nucleus can have up to 2 electrons. The second shell from the nucleus can have up to 8 electrons. The third shell can have up to 18 electrons. The fourth shell can have up to 32 electrons. Bohr’s Model Copper (Cu) atom

12. Maximum electrons 1 st energy level = 2 2 nd energy level = 8 3 rd energy level = 18 4 th energy level = 32

13. Periodic Table See the number of electrons for each energy level.

14. Size of atom atomic mass unit (amu,  ) = unit for mass on the atomic scale

15. Mass of subatomic particles proton ~ 1 amu neutron ~ 1 amu electron is tiny (Who cares?)

16. mass number Number of protons + number of neutrons

17. atomic weight Aka: average atomic mass The weighted average of the masses of the naturally occurring isotopes of an element The other number on the periodic table (unit = amu)

18. Atomic weight is close to the mass number for the most common kind of atom of that element.

19. Calculate number of neutrons Example: bromine (#35) Mass number = 80 Atomic number = 35 = protons Neutrons = 80 - 35 = 45

20. Calculate number of neutrons Example: strontium (#38) Mass number = 88 Atomic number = 38 = protons Neutrons = 88 - 38 = 50

21. Assignment Example Bromine symbol = Br Mass number = 80 Atomic number = 35 Number of protons = 35 Number of neutrons = 80 – 35 = 45

22. Assignment Example Bromine continued Number of energy levels = 4 Skip period and group columns today.