1. Atoms: Building blocks
Start a new page of notes:
Draw a large line across where you stopped last time
Write Chapter 3 at the top of the page and put a box around it
Chapter 3
Atoms: Building blocks
Atom: the smallest particle of an element that retains its identity in a chemical reaction

2. Seeing is NOT always believing…
When you can’t see what you are studying, it helps to obtain experimental data to help understand the “picture”.
Matter is composed of particles that are not visible to the naked eye…these particles are called ATOMS.

3. Notes on notes Titles are important!!!
Make them visible: highlight, underline, box…
If you are absent, you still have to get the notes from a friend or online.

4. Reaction mass demo: Is there a significant difference in the mass?
What happened to the baking soda?
Weight Before
Weight After
Difference in weight

5. Conservation of mass NaHCO3 + HC2H3O2 → NaC2H3O2 + H2O + CO2
Mass is neither created or destroyed during ordinary chemical reactions
NaHCO3 + HC2H3O2 → NaC2H3O2 + H2O + CO2

6. NaHCO3 + HC2H3O2 → NaC2H3O2 + H2O + CO2
Law of definite proportions: Compounds combine in fixed ratios ex: CO2 or NaCl
Law of multiple proportions: Compounds are composed of whole number ratios

7. The Atomists: these people all helped transform our ideas about nature.
Aristotle
Democritus
John Dalton
JJ Thomson
Rutherford:
Robert Millikan:
Write each name on your paper, skipping at least -2 line between each to take notes.

8. Aristotle: thought matter couple be divided forever (he was believed for a while) Democritus: disagreed, thought atom was smallest particle. He was correct!
boulder
Large rocks
Smaller rocks
pebbles
sand
dust
460 BCE: Greek Democritus suggested that matter is “ composed of minute, invisible, indestructible particles of pure matter which move about eternally in infinite empty”

9. John Dalton: said matter is made of tiny particles called atoms that cannot be divided - All atoms of same element will be exactly the same - Had no microscope to see this!
John Dalton ( ), an English schoolteacher and chemist,
Dalton proposed his atomic theory of matter in 1803.

10. Dalton’s Atomic Theory (add notes below your people)
All matter is made up of atoms.
All atoms of one element are exactly alike, but differ from other elements.
Atoms can’t be subdivided, created, or destroyed
Atoms mix in simple whole number ratios to form compounds.
Chemical reactions happen when atoms are separated, joined, or rearranged.
* Atoms of one element can NEVER be turned into atoms of a different element!

11. Modern Change to Dalton’s Theory…
Atoms are NOT indivisible!
Atoms can be broken into three subatomic particle:
Electrons
Protons
Neutrons

12. Check:
What did Dalton get right and how was her wrong?

13. Review Electrons Protons Neutrons Dalton’s Atomic Theory (shortened)
All matter is made of atoms
All Na atoms are the same but are different from He atoms
Atoms can’t be divided, created, destroyed
Atoms mix in whole number ratios
Chemical reactions happen when atoms are separated, joined, or rearranged
Atoms are NOT indivisible!
Atoms can be broken into three subatomic particle:
Electrons
Protons
Neutrons

14. Discovery of the Electron
Because of Dalton’s atomic theory, most scientists in the 1800s believed that the atom was like a tiny solid ball that could not be broken up into parts.
JJ Thomson:
Discovered the electron: used cathode ray tube
Determined - electrons and + protons
Plump pudding model
In 1897, a British physicist, discovered that this solid-ball model was not accurate.

15. Cathode-Ray Tube + - Voltage source
Cathode-Ray Tube
Cathode Ray: a stream of electrons produced at the negative electrode of a tube containing a gas at low pressure
Thomson knew that objects with like charges repel each other, and objects with unlike charges attract each other
Voltage source + -
By adding an electric field…he found that the moving pieces were negatively charged!

16. Thomson named the negative particles found in his experiment electrons.
You don’t get shocked when you touch EVERYTHING
So … there must be something positively charged in the atom to balance the electrons.

17. Plumb Pudding Model:
A bunch of positive “goo”, with the electrons embedded in it that could be removed
Thomas couldn't’t find positive counterpart (but knew it had to exist since matter is electrically neutral)

18. At this point, it seemed that atoms were made up of equal numbers of electrons and protons
However, in 1910, Thomson discovered that neon consisted of atoms of two different masses
Because of neutrons!
More on this later! 

19. gold foil experiment: disprove plump pudding
Rutherford:
gold foil experiment: disprove plump pudding
atom is mostly empty space, containing small positive nucleus
1909

20. Since most of the particles passed through the foil, they concluded that the atom is nearly all empty space. Atoms have a center, positive nucleus!

21. determine electron charge
Robert Millikan:
oil drop experiment
determine electron charge
Since he was able to work out the mass of the oil drop, and he could calculate the force of gravity on one drop, he could then determine the electric charge that the drop must have. By varying the charge on different drops, he noticed that the charge was always a multiple of -1.6 x C, the charge on a single electron. This meant that it was electrons carrying this unit charge.

22. The Nuclear Model of the Atom:
Nucleus: small, dense, positive center of protons and neutrons
Contains most of the mass of the atom (protons and neutrons)
Is very small compared to the rest of the atom
the atom has a small, dense, positively charged central core, called a nucleus.
IF the atom was the size of a stadium, the nucleus would be the size of a rice grain.

23. C. Neutrons (n0): D. Electron (e-) B. Protons (p+): Neutral charge
Positively charged, fixed subatomic particles (+1)
Mass of 1 amu (1 proton = mass 1840 electrons)
Very, very heavy when compared to electrons
C. Neutrons (n0):
Neutral charge
Mass of 1amu
Can change amount in atoms
D. Electron (e-)
Negative charge, no mass
Orbits nucleus
Can change in atoms

24. The Evolution of Atomic Theory

25. Modern View
The atom is mostly empty space w/ electron cloud - region where you might find an electron

26. How do you figure out the # of protons?
Elements are different because they have different numbers of protons
How do you figure out the # of protons?

27. Elements are electrically neutral
Elements are electrically neutral. (no charge) Neutral atom: # of negatively charged particles = # of positively charged particles
So if the atomic number is the number of protons …..
Then it must also be the number of electrons in order to balance the atom
#protons = # electrons in a neutral atom

28. Practice What is the atomic number of carbon?
How many protons?
How many electrons?
What is the atomic number of aluminum?

30. How to get the info from the periodic table
Atomic Number:
Number of protons in the nucleus of the atom. 1
Atomic Mass:
Average mass of all isotopes of that element.
protons+ neutrons
1.0013
Hey, why isn’t this a whole number?

31. Saving paper is always good!
Name
Per, Row
Warm-ups 2 1. 2.
10/1/14
10/3/14
Saving paper is always good!

32. Warm up Write the symbol for protons, neutrons and electrons.
How many electrons does Mg have?
Draw a representation of a lithium atom?

33. Isotopes So why the difference in mass?
Atoms of an element that are chemically alike but differ in mass
So why the difference in mass?
Differ in # of neutrons
Because of the discovery of isotopes, scientists hypothesized that atoms contained still a third type of particle that explained these differences in mass.
What was that particle?

34. Two isotopes of sodium.

35. What is a weighted average?
Think about how your grade is calculated….
Average atomic mass: average mass of the relative abundance of the isotopes
- this is what is shown on the periodic table!

36. How many subatomic particles?
# protons = atomic number (always)
For a NEUTRAL atom # electrons=# protons
(this will be a bit different in upcoming later…)
# neutrons = mass number - # protons (always)

37. In this chapter you will fill out lots of tables…
Name
Protons
Electrons
Mass
Neutrons
Helium 2 4
4-2 = 2
Carbon-12 6 12
12-6 = 6
Carbon-13 13
13-6=7      
Carbon-12 and Carbon-13 are isotopes

38. Answer these ?’s What is the atomic number of Li?
What is the mass number of Li?
How many p+ in Li?
How many e- in Li?
How many neutrons in Li?

40. Answer these ?’s
Atomic # = 3
Mass # = 7
p+ = 3
e- = 3
no = 4

41. Symbols
The symbol of the element can show the mass number and the atomic number.
Atomic mass: average of isotopes
Mass #: mass of a specific isotope (proton=neutron)
Atomic Symbol nuclear symbol
Atomic #
Mass #
Atomic #
Atomic mass
The mass # is the bigger number!

42. Al 27 13 Find the number of protons number of neutrons 13
number of electrons
Atomic number
Mass Number 13 13
27-13 = 14 27

43. Mass #
Atomic #

44. More on Isotopes Many elements have an isotope…
That is why you see the average atomic mass as a decimal value on the periodic table.
Naming an Isotope: Put the mass number after the name of the element
Ex: Carbon- 12
Carbon -14
Hg Hg - 180

46. Ions An ion is an electrically charged atom or group of atoms.
A normal atom is electronically neutral because it has the same number of electrons ( - ) as protons ( + )
Anion: gains more electrons causing - charge
Cation: loses electrons causing + charge

47. 13 13
Al3-
Naming an ion: use superscript with number then charge ex: Cation: Na+ Mg2+ Anion: Cl- Te2-

49. Ion-Bean Activity

50. Warm Up p+ e- n0 Nuclear symbol 34 36 44 Ca2+ Compete the table:41 20
Compete the table:
How would you name the isotope of Ca shown in the table?
How would you name the ion of the element with 34p+ shown in the table?

51. Warm Up p+ e- n0 Nuclear symbol 34 36 44 Se2- 20 18 21 Ca2+78 34 41 20
Compete the table:
How would you name the isotope of Ca shown in the table?
Calcium-41
How would you name the ion of the element with 34p+ shown in the table?
Se2-

52. Ch 21: nuclear chemistry How does the nucleus stay together?
Add to your notes! Don’t forget to make the title clear and visible
How does the nucleus stay together?
Strong nuclear forces: hold protons and neutrons together
-overcome positive charges
- stronger than gravity! But short distance
The nucleus of an atom is held together by the strong nuclear force that binds together protons and neutrons. Although the strong nuclear force is the strongest of the four fundamental forces, it acts only over very short - typically nuclear - distances. It binds together the protons and neutrons in the nucleus. It also holds together the quarks that make up those protons and neutrons and the other hadrons.
Other 3 fundamental forces gravity, the electromagnetic force, and the weak nuclear force
Nuclear Reaction: changes nucleus- usually releases energy

53. Nuclear Reaction: changes nucleus- usually releases energy
Nuclear reactions-
In the late 1890s scientists noticed that some substance spontaneously emitted radiation in a process they called radioactivity.
It turns out they were going through nuclear reactions which involves a change in an atom’s nucleus, thus altering it’s identity.
It takes a lot of energy to start a nuclear reaction (to overcome nuclear forces), but even more energy is released once it starts.

55. Radiation: when an unstable nuclei gains stability by losing energy
Why do radioactive atoms emit radiation?
Unstable due to too many neutrons
Unstable systems gain stability by losing energy.

56. Being in a handstand (scorpion) position is an unstable state
Being in a handstand (scorpion) position is an unstable state. Like unstable atoms, people doing handstands eventually return to a more stable state-standing on their feet-by loosing potential energy.

57. What is the half life (in years) of the strontium shown in the graph.
Warm Up
What is the half life (in years) of the strontium shown in the graph.
How much Sr will remain after 2 half lives?
If the half life of radium is 30 minutes, how much radium would be left in a particle sample after 1.5 hours.

58. What is the half life (in years) of the strontium shown in the graph.
How much Sr will remain after 2 half lives?
If the half life of radium is 30 minutes, how much radium would be left in a particle sample after 1.5 hours.
30 years
25%
1.5 hours = 3 half lives, cut 1000 in half 3 times = 250 particles

59. Half life: time it take for half of the atoms of a element to decay
Half Life: used for finding the age of samples
Half life: time it take for half of the atoms of a element to decay
-releases radiation can even becomes other elements

60. 3 Types of Radiation Alpha radiation: largest and weakest
pair of neutrons and a pair of protons
Not very dangerous, stopped by clothes
Beta radiation, medium size and strength
electrons that move very quickly
Gamma radiation: smallest, strongest, most dangerous
Similar to x-rays
extremely high energy photons (pure energy wave)
Alpha particles are commonly emitted by all of the larger radioactive nuclei such as uranium, thorium, actinium, and radium,
Beta emission occurs in elements with more neutrons than protons, so a neutron splits into a proton and an electron. The proton stays in the nucleus and the electron is emitted. 

61. Other radiation Other forms of radiation from Electromagnetic waves:
Microwaves
X-rays
Radio waves

62. Japan nuclear power plant disaster
earthquake-nuclear-power-reactor-damaged-high- radiation/story?id=

63. Half Life: The measure of how fast an atom decays
Every radioactive substance will decay .
Half Life: The measure of how fast an atom decays
After each half life, half of the radioactive atoms become a new element.

64. Nuclear Fission Fission—when the nucleus of an atom breaks apart.
Starts with an initial hit of the nucleus with a neutron.
Releases A LOT of energy…1 kg of U = 20,000 tons of TNT
Controlled fission = nuclear power
Uncontrolled fission = bomb

65. Fusion Fusion-when the nuclei of atoms combine Ex: Sun’s energy
Only occurs at very high temperatures (>40,000,000°C)
Releases A LOT of energy…even more than fission
Is this currently an energy option on Earth? No
Why?
Ex: Sun’s energy
Not currently controllable to create on earth
This is how the sun provides energy!
Hydrogen and Helium ions plasma need to be moving at extreme speeds and at extreme temperatures. So it needs to be controlled very carefully or else a fusion reactor would melt. Also, it is too hard and dangerous to sustain that temperature in present reactors so it would not be reliable and energy companies will lose money because starting the reactor takes too much energy.

66. Uses of Radiation Use of Radioisotopes: for dating (carbon dating)
Medicine- tracer, identifying
Can follow the course of an element through a chemical reaction
E.g. using radioactive carbon-14 isotope to study glucose formation in photosynthesis
6CO2 + 6H20  C6H12O6 + 6O2
Iodine-131 used to detect diseases in the thyroid gland
With proper safety procedures, radiation can be useful in many scientific experiments and industrial applications.

67. Uses of Radiation, con’t
Treating cancer
All cancers are characterized by rapid growth of abnormal cells
Radiation therapy is used to treat cancer by destroying cancer cells
Downside is that some healthy cells are affected too
PET scan: the active part glows!
Positron Emission Transaxial Tomography (PET)
Radiotracer that decays by positron emission is injected into patient’s bloodstream. Create image of beta radiation

68. Biological Effects of Radiation
Burns
Cancer
Damage reproductive tissue (especially in children)
Can ionize molecules within biological tissue
Damages to bodies depends on…
Type of Radiation
Energy
Type of tissue absorbing the radiation
Penetrating power of radiation
Distance from source

69. Videos Cherynobl Part I Cherynobl Part II Cherynobl Part III
children of Cherynobl
radioactive-decay-and-their-effect-on-the- nucleus.html#lesson

71. THE END 