1. Atoms!!!!
Chapters 4.1, 5.1, 4.2, 4.3, 4.4, 4.5

2. What are Atoms?
Atoms are very tiny particles that form the building blocks for all matter

3. Just What Size Is an Atom?
Let’s do a little exercise!!
What you’ll need
A strip of paper
A pair of scissors
DON’T DO THIS YET!
Here is what to do …
Take your strip of paper and cut it into equal halves
Cut one of the remaining pieces of paper into equal halves
And so on …

4. Just What Size Is an Atom?
Cut 1
Pocket
Hand
14 cm

5. Just What Size Is an Atom?
Cut 2
Finger
Ear
7.0 cm

6. Just What Size Is an Atom?
Cut 3
Watch
Mushroom
Eye
3.5 cm

7. Just What Size Is an Atom?
Cut 4
Keyboard Key
Ring
Insect
1.75 cm

8. Just What Size Is an Atom?
Cut 5
Keep going … atoms are much smaller!
0.88 cm

9. Just What Size Is an Atom?
Cut 6
Tiny seeds on top of a Whopper bun
0.44 cm

10. Just What Size Is an Atom?
Cut 7
Keep going … atoms are still much smaller!
0.22 cm

11. Just What Size Is an Atom?
Cut 8
Thread
1.0 mm

12. Just What Size Is an Atom?
Cut 9
It’s too difficult to keep cutting!
Let’s just pretend from now on
0.5 mm

13. Just What Size Is an Atom?
Cut 10
The size of one tiny light (pixel) on a computer screen
0.25 mm

14. Just What Size Is an Atom?
Cut 11
Wow, I didn’t think anything was this small!
0.125 mm

15. Just What Size Is an Atom?
Cut 12
A piece of hair
0.06 mm

16. Just What Size Is an Atom?
Cut 13
Our meter has disappeared!
???
0.03 mm

17. Just What Size Is an Atom?
Cut 14
The width of paper
0.015 mm

18. Just What Size Is an Atom?
Cut 15
We’re not done yet keep cutting!
0.007 mm

19. Just What Size Is an Atom?
Cut 16
Bacteria
0.003 mm

20. Just What Size Is an Atom?
Cut 17
We’re not done yet keep cutting! mm

21. Just What Size Is an Atom?
Cut 18
Water filter
1.0 micron

22. Just What Size Is an Atom?
Cut 19
We’re not done yet keep cutting!
0.5 micron

23. Just What Size Is an Atom?
Cut 20
Tiny wires inside a computer chip
0.25 micron

24. Just What Size Is an Atom?
Cut 21
We’re not done yet keep cutting!
0.13 micron

25. Just What Size Is an Atom?
Cut 22
Virus
0.07 micron

26. Just What Size Is an Atom?
Cut 23
We’re not done yet keep cutting!
0.03 micron

27. Just What Size Is an Atom?
Cut 24
We’re not done yet keep cutting!
0.015 micron

28. Just What Size Is an Atom?
Cut 25
We’re not done yet keep cutting!
0.008 micron

29. Just What Size Is an Atom?
Cut 26
Almost there
5 Cuts left
0.004 micron

30. Just What Size Is an Atom?
Cut 27
Almost there
4 Cuts left
0.002 micron

31. Just What Size Is an Atom?
Cut 28
Almost there
3 Cuts left
0.001 micron

32. Just What Size Is an Atom?
Cut 29
Almost there
2 Cuts left
micron

33. Just What Size Is an Atom?
Cut 30
Almost there
1 Cut left
micron

34. Just What Size Is an Atom?
Cut 31 H Ca He
Atoms !!! Cl C Na O N
micron

35. Atom Facts A sheet of paper is about 10,000 atoms thick
There are about 2,000,000,000,000,000,000,000 (that’s 2 thousand billion billion) oxygen atoms in a small drop of water. There are twice that many hydrogen atoms.

37. Objectives
I will know where metals, nonmetals and inert gases are found on the periodic table.
I will know that each element has a specific number of protons in the nucleus and that this is the same as the atomic number.

38. Objectives
I will know what an isotope is and that isotopes of an element have a different but specific number of neutrons in the nucleus.
I will know that substances can be classified (sorted) by their properties such as melting points, densities, hardness, thermal conductivity (how well heat travels through the substance) and electrical conductivity (how well electricity travels through the material).

39. Chapter 4.1
Introduction to Atoms

40. Development of the Atomic Theory
The development of the modern atomic theory shows how a theory is based on experimental evidence, but is modified, as more evidence is collected.

41. Development of the Atomic Theory
The 1st people to think about the nature of matter were the Greeks in 430 B.C.
Democritus proposed that the idea of matter is formed of small pieces that could not be cut into smaller parts.
He used the term atomoV (atomos) which means “uncuttable” for the small pieces.

42. Democritus
Weird
He also thought that sweet tasting objects have smooth atoms, sour tasting objects have sharp atoms
In modern terms, an atom is the smallest particle of an element.
“Nothing exists but atoms and empty space, everything else is opinion ---”

43. Atomic Theory Continued…
Atomic theory grew as a series of models that developed from experimental evidence. As more evidence was collected, the theory and models were revised.
Many scientists were involved in the development of the atomic theory.
John Dalton
J.J. Thomson
Ernest Rutherford
Niels Bohr

44. John Dalton John Dalton (1766-1844) British School Teacher
First to do research on color blindness (he was color blind)
Did independent research in his laboratory

45. John Dalton
John Dalton was an English chemist and inferred that atoms had certain characteristics.
Dalton’s ideas included:
All elements are composed of atoms that cannot be divided.
All atoms of the same element are exactly alike and have the same mass.
An atom of one element cannot be changed into the atom of a different element.
Atoms cannot be created nor destroyed in any chemical reaction, only rearranged.
Every compound is composed of atoms of different elements, combined in a specific ratio.

46. J.J. Thomson
In 1897, J.J. Thomson (another English scientist) found that atoms contain negatively charged particles (electrons).
Thomson also proposed, based on other’s experiments, that atoms must also contain some sort of a positive charge.
Thomson describes an atom that consists primarily of negative charges scattered throughout a ball of positive charge (like raisins in a muffin, or plums in pudding).

47. Ernest Rutherford Ernest Rutherford was a student of J.J. Thomson.
In 1911, Rutherford, with the help of his research team aimed a beam of positively charged particles at a thin sheet of gold foil.
He predicted that the charged particles would pass through the gold foil in a straight line, however he noticed that some of the particles were deflected strongly!
Rutherford inferred from this that an atom’s positive charge (protons) must be clustered in a tiny region in its center, called the NUCLEUS!

48. Rutherford’s Gold Foil Experiment
Rutherford was surprised that a few particles were deflected strongly. This led him to propose an atomic model with a positively charged nucleus.

49. Niels Bohr
In 1913, Niels Bohr, a Danish scientist, showed that electrons could have only specific amounts of energy causing them to move in certain orbits (similar to how the planets orbit the sun).

50. The Bohr Model

51. The Cloud Model
In the 1920’s, scientists determined that electrons do not orbit the nucleus like planets, instead electrons can be anywhere in a cloudlike region around the nucleus.
This was known as the “cloud” model and explains that an electron’s movement is related to its energy level.
Electrons of different levels are likely to be found in different places within the atom.

52. The Modern Atomic Model
In 1932, English scientist James Chadwick discovered another particle; the neutron.
This new particle was hard to discover because it had no charge, thus was named the neutron!
The new atomic model explains that at the center of the atom is a tiny, massive nucleus containing protons and neutrons. Surrounding the nucleus is a cloudlike region of moving electrons.

53. All About the Atom… An atom is composed of 3 charged particles:
The proton (+ positively charged)
The electron (- negatively charged)
The neutron (0 no charge)
Every atom contains a nucleus made up of both protons (+) and neutrons (0).
Around the nucleus are electrons (-) at different levels depending on their specific energy.

54. Particle Charges
The charges in an atom balance, making the atom neutral.
The number of protons and electrons must be equal so that the charges balance.
Neutrons do not have to equal the number of protons because they have no charge.

55. Particle Masses
Even though electrons balance protons charge-for-charge, they are not the same size.
Electrons are so small that it takes almost 2,000 electrons to equal the mass of just one proton.
Protons and neutrons are about equal in mass.

56. Size of Atoms
Atoms are incredibly small, you can’t see them with the naked eye or even a microscope!
Even our most advanced microscopes can’t show the structure of atoms, they can only give of glimpse of what they might look like!
If the nucleus was the size of your pencil eraser and you placed it on the pitcher’s mound of a baseball stadium, the electrons could be as far away as the top row of seats!

57. Atomic Number (page 134)
Every atom of a given element has the same number of protons.
Example: every oxygen atom has 8 protons and every iron atom has 26 protons.
The number of protons in the nucleus of an atom is the atomic number of that atom’s element.
The definition of an element is based on its atomic number.

58. Chemical Symbol
Every atom of a given element has a specific chemical symbol
The chemical symbol is an abbreviation of the element’s name either in Latin or English
Cu = Copper or cupric
K = Potassium or kelium
C = Carbon
Li = Lithium

59. Isotopes and Mass Number
Even though the number of protons is fixed for a particular element, the number of neutrons are not.
Atoms of the same element can have different numbers of neutrons in the nucleus.
These atoms are called isotopes.
Some isotopes are very unstable and are classified as radioactive elements.

60. Isotopes and Mass Number
Some isotopes are more common than other isotopes.
Example: Carbon-12 is more common than Carbon-13, Carbon-14
Despite the differences in mass, all carbon isotopes react the same way chemically!
Mass Number is the sum of the protons and neutrons in the nucleus of an atom.

61. Atomic Mass
The atomic mass is the average mass of all the isotopes of an element
(It is approximately the same as the number of protons and neutrons in the nucleus of an atom).

62. The Hydrogen Atom 1H One electron orbiting a nucleus
1 proton = atomic number
0 neutrons = 0
Total mass = protons + neutrons =1 p e 1H

63. The Helium Atom 4He Two electrons orbiting a nucleus
2 protons = 2 = atomic number
2 neutrons = 2
Total mass = 4 = Protons + Neutrons = atomic mass e p n n p e
4He

64. Isotopes and Elements 3H (Tritium) 3He
If Helium loses one of its protons (and one of its electrons), it becomes a different element p n n
3H (Tritium) p n e
If Helium loses one of its neutrons, it becomes an isotope
3He

65. How new elements.atoms are made