Everything is made up of something The topic of chemistry studies what those some things are.

2. Everything is made up of something • The topic of chemistry studies what those some things are. • Chemistry studies Matter, which is anythign that has mass, and takes up space

3. People used to think that the orld was made up of 4 principal building blocks • Earth • Water • Fire • wind

4. Dalton • IN the 1700’s a teacher in Engalnd began to think that everything was up of small building blocks that we couldn’t see. • He called these building blocks atoms

5. He also explained that different materials got their differences because they were made up of different building blocks, or different atoms. • But all basic building blocks (Atoms) of the same type were exactly the same.

6. Atomic Theory • His theory can be explained in 4 simple points • All elements are made of tiny atoms we cant see • All atoms of the same elements are identical even if they came from different places

7. 3- Atoms of different elements are different. This means that the reason gold is different then silver is because its atoms are different. 4- Many new materials are made when atoms of different elements mix together, these are called compounds.

8. What is an atom made of • Dalton said atoms are he smallest thing, he was almost right. • The atom is actually made of smaller pieces called Sub-Atomic particles. • (Sub means under, so sub atomic means under the atom, or inside the atom)

9. The Electron • The first subatomic particle discovered was the electron. • This was discovered by J.J. Thompson he used a cathode ray tube

11. He discovered that when he added a battery to opposite ends of the tube, it created a beam that would be repelled by negative magnets, • And attracted to positive magnets. (Show movie on cathode raye

12. If there are negative charges…… • Once it was discovered that all atoms have tiny particles of negative charge (electrons) it was reasoned there must also be positive charges. • This was needed to make the overall atom neutral.

13. Where are the positive atoms • People first thought the negative charges were embedded in the atom, with positive charges all around them • This was called the plum pudding model

15. There was a scientist named Earnest Rutheford. • He performed an experiemtn to see where the positive and negative charges were. • He performed the Gold foil experiemtn

16. He took radioactive material and directed the beam of radiation (Which had a positive charge) at a sheet of gold foil. This beam was called alpha particles • He also had radioactive paper behind the gold to see where the particles deflected.

18. What he found • He found that almost all of the particles he shot at the gold went right through, but a few were deflected. • They were deflected a lot!

19. He reasoned that the positive charges in the atom were deflecting his radioactive alpha particles. • But 99% of his alpha particles got through. • But the ones that were deflected were really deflected

20. He deduced that the atom was mostly empty. • This was why most alpha particles got right through. • But the positive charges inside were very dense.

21. He called these positive charges protons, • He hypothesized they must be clustered tightly in a small part of the atom called the Nucleus • (show movies on gold foil experiment)

22. Problem • If there were only lots of positive charges (protons) in the nucleus very tightly packed wouldn’t they repel each other like magnets of the same charge. • There must be something in the nucleus, but in between the protons to space them out.

23. It was later discovered that in fact there were neutral particles in the nucleus, and that they were stuck in between the protons to space them out. These particles are called neutrons. Because they have no charge, they are neutral.

26. Recap • Lets re-cap what we know • Protons are + • Nuetrons have no charge • They both live in the nucleus

27. Electrons go around the Nucleus and have a negative charge. • Also the atom is mostly empty space

28. More on electrons • Electrons can orbit the nucleus at different distances. • The farther away an electron gets the weaker it is held by the positive nucleus. • This means that the farther away an electron is the more energetic it is.

29. Each orbit level can hold a set number of electrons. • The first level holds 2, the next holds 8, the next hold 18.

31. The rule of electrons is that electrons must fill up a lower level before they can fill up a higher level. • This is called Aufbau’s rule.

32. Valence electrons • If an atom has 11 electrons that means it will have 2 electrons in level #1 • 8 in level # 2 • And 1 electron in level # 3 • These electrons in the last level are called Valence electrons

33. Orbitals • Electrons don’t really go around the nucleus in a nice simple circle, even though we draw it that way. • Electrons orbit in very complicated ways. • The place that electrons are likely to be found is called an orbital

35. Atomic Weights • A protons and a neutron weight the same amount. • They both weigh .00000000000000000000000000167 grams

36. This number is to small and is hard to remember. • Instead we say a proton and neutron weigh 1 Atomic Mass Unit (AMU) • Electrons are much muchmuch smaller!!

37. Atomic number • On the periodic table we arrange elements by the number of protons they have. • The number of protons something has is called it’s atomic number. • It is the bold number on the periodic table.

38. Atomic number • Each & every atom of the same element must have the same number of protons. • Meaning they must have the same atomic number. • Ex. If chlorine has 17 protons it must have an atomic number of 17.

39. Atomic mass • The number of protons an atom has plus the number of neutrons something has is called the atomic mass. • Ex. If a chlorine has 17 protons and 16 neutrons it has an atomic mass of 33.

40. Atomic mass • Many times we will not be told the number of neutrons an atom has. • But if we know the atomic number and atomic mass we can determine the number of neutrons

41. Atomic mass • Determine the # of neutrons of an oxygen atom with an atomic mass of 17. • Hint oxygen is O on the periodic table.

42. Isotopes • Even though every single atom of the same element must have the same number of protons, they can have different number of neutrons. • Ex. Every carbon has 6 protons, but some may have 6 neutrons and some may have 7. etc.

43. Isotopes • If we have 2 atoms of carbon both with 6 protons, but different numbers of neutrons, they called isotopes of each other. • Isotopes are atoms with the same protons and different neutons.

44. Isotope symbols • As soon as I say carbon you can know it has 6 protons. • But you don’t automaticlly know how many neutrons it has.

45. So to say a carbon with 6 neutrons we say Carbon-12 or C-12 The number after the symbol tells us the atomic mass.

47. Examples • Find the number of Neutrons in: • C-12, C-13, & C-14 • Nitrogen- 13, & Nitrogen-15 • Lithium-6 & Lithium-5

48. Average Masses • If you take 10 tests… • If you get an 90 on 7 of them • A 55 on 1 • And a 85 on 2 • How can we find the average?

49. Average masses • Should we take the time to add them all up and then divide by 10? • An easier way is to find the percentages of each & multiply by the grade.

50. .7 X 90=63 • .1X 55=5.5 • .2 X 85 =17 • Then we add them all= 85.5