1. Atoms and the Periodic Table Chapter 17 page 506

2. Structure of the Atom An atom is made up of smaller particles called subatomic particles. These are – Protons – positive charge Neutrons – no or neutral charge Electrons – negative charge

3. Atom Center is called the nucleus. Nucleus contains the protons and neutrons. Electrons fly in a cloud around the nucleus.

4. Atoms on the PT The atomic number indicates the number of protons in the nucleus. Atomic mass indicates the average sum of the protons and neutrons.

5. History of the Atomic Model Democritus – 4 th century BC philosopher Suggested the world was made of invisible units He called them atoms. Atom – Greek meaning unable to be divided Although his theory explained things, he couldn’t provide any evidence.

6. John Dalton In 1808 an English schoolteacher came up with a theory that was developed with a scientific basis. Today, his theory is the foundation of modern atomic theory.

7. Dalton’s Theory Matter was made up of atoms that could not be divided. All atoms of a given element are exactly the same. Atoms of given elements could join to form compounds. Because he could provide scientific proof, people believed him.

8. More Theories In 1877 JJ Thomson theorized on particles smaller than an atom.  Electrons In 1911 Ernest Rutherford theorized a nucleus in an atom with a positive charge.

9. Niels Bohr In 1913 this Danish scientist proposed a model of the atom where electrons moved in definite orbits around the nucleus. Like planets around the sun.

10. Atomic Models Today the atomic models is based on waves. This means electrons do not travel in set paths around the sun. All we can tell is where an electron is most likely to be found.

11. Today Please take out: –periodic table, –Anatomy of an Atom Worksheet –Worksheet packet –Notebook.

12. Drawing an Atomic Model First – number of protons is atomic number Number of neutrons is atomic mass (rounded) - atomic # Electrons are also equal to atomic number

13. Electrons First energy level holds 2 electrons. Second orbital holds 8 Third holds 18, fourth 32,

15. Atomic Modeling First place electrons equal to the number of protons, Now you must adjust according to the octet rule. All atoms want to have eight electrons or complete orbitals in their highest energy level. Add or take away electrons according to this rule.

16. Atomic Model cont. Now adjust the charge of the atom accordingly. You’ll end with a positive # if you took away electrons, negative if you added. Try one. Ne, atomic # 10 atomic mass of 20

17. Isotopes Atoms of the same element having different numbers of neutrons. Sodium – It’s atomic mass is 22.98. So it can have a mass of 22 or 23. How many neutrons is in Sodium-23? Sodium- 22? Which one occurs more often?

18. Counting Atoms During chemical reactions you need to know how many atoms are involved. Remember, more than one element bonded together is a compound. – H 2 O

19. Counting Atoms cont. O 2 = two Oxygen atoms bonded together. It’s now a molecule. The 2 is called a subscript. 7H 2 O The 7 is called a coefficient. This means there are 7 water molecules, each molecule having 2 Hydrogens and one Oxygen

20. Counting Atoms cont. CO 2 - How many Carbon atoms are present? How many Oxygen atoms? 3SO 4 How many Sulfer atoms? How many Oxygen atoms? How many protons?

21. Practice! S(H 2 0) 2 S = 1 H = 4 O = 2 12H 2 SO 4 8Na 2 (OH 4 ) 6 10C 6 H 12 O 6 (OH) 12

22. 3(Mg,Fe) 7 Si 8 O 22 (OH) 2 Fukalite - 7Ca 4 Si 2 O 6 (CO 3 )(OH,F) 2 Periodic Acid – 12H 5 IO 6