1. Name a scientist that you remember and tell for what he/she is known, did, or discovered. Give any other information you can such as branch of science, prizes won, country of origin, etc.

2. Atomic Structure
Defining the Atom

3. Eureka - Atoms

4. Meet the Elements Video clip

5. What is an Atom?
The smallest part of an element that retains its identity in a chemical reaction.

6. Atomic History

7. (greek for indivisible)
HISTORY OF THE ATOM
Democritus develops the idea of atoms
460 BC
he pounded up materials in his pestle and mortar until he had reduced them to smaller and smaller particles which could not be divided and called these:
ATOMA
(greek for indivisible)

8. Historic Models of the Atom
Aristotle ( BC) didn’t think there was a limit to the number of times matter could be divided.
He knew there were small particles. Air, Fire, Earth, Water

9. HISTORY OF THE ATOM ATOMS John Dalton 1808
suggested that all matter was made up of tiny spheres that were able to bounce around with perfect elasticity and called them
ATOMS

10. Dalton’s Atomic Theory
All elements are composed of atoms (which can’t be divided).
Atoms of the same element have the same mass and atoms of different elements have different masses.
Compounds contain atoms of more than one element.
In a compound, atoms of different elements always combine in the same way.

11. Dalton’s atom

12. Dalton’s Atomic Theory
Most of Dalton’s statements are now known to be flawed.
As we continue to study the atom, we will talk about discoveries that disproved Dalton’s statements.
Scientists have revised the theory due to new discoveries!

13. HISTORY OF THE ATOM ELECTRON Joseph John Thomson 1898
found that atoms could sometimes eject a far smaller negative particle which he called an
ELECTRON

14. J.J. Thomson, 1897
Discovered the electron, the subatomic particle with a negative charge
His experiments involved the use of a cathode ray tube
Animation of
Thomson’s model

15. JJ Thomson Question and explanation on youtube

16. JJ Thomson Video clip
Start at 5:00 and go to about 7:00

17. HISTORY OF THE ATOM PLUM PUDDING MODEL 1904
Thompson develops the idea that an atom was made up of electrons scattered unevenly within an elastic sphere surrounded by a soup of positive charge to balance the electron's charge
like plums surrounded by pudding.
PLUM PUDDING
MODEL

18. Thomson’s Atomic Model
Developed the Plum Pudding model. (think of a chocolate chip cookie)
Electrons evenly distributed throughout a positively charged material.

19. Plum Pudding Model
e e-
e e- e-
Sphere of
Positive charge

20. HISTORY OF THE ATOM Ernest Rutherford 1910
oversaw Geiger and Marsden carrying out his famous experiment.
they fired Helium nuclei at a piece of gold foil which was only a few atoms thick.
they found that although most of them passed through. About 1 in 10,000 hit

21. HISTORY OF THE ATOM
gold foil
helium nuclei
helium nuclei
They found that while most of the helium nuclei passed through the foil, a small number were deflected and, to their surprise, some helium nuclei bounced straight back.

22. Ernest Rutherford, 1911
Tested theory that electrons were evenly distributed throughout the atom within positively charged material
Performed the Gold-Foil Experiment

23. Rutherford animation

24. Another Rutherford Animation

25. Ernest Rutherford
If Thomson’s model was correct, most of the alpha particles should pass through with a little deflection

26. Rutherford’s Model
Proposed that atoms contain a nucleus, a small, dense, positively-charged sphere in the center of the atom.
Atom contains mostly empty space.
The nucleus is tiny compared with the atom as a whole.

27. Ernest Rutherford
Thomson’s model
Rutherford’s model

28. Rutherford’s model: Nuclear Atom
e e- e- +
+ +
Rutherford did NOT know about neutrons!

29. HISTORY OF THE ATOM However, this was not the end of the story.
Rutherford’s new evidence allowed him to propose a more detailed model with a central nucleus.
He suggested that the positive charge was all in a central nucleus. With this holding the electrons in place by electrical attraction
However, this was not the end of the story.

30. The Houston Astrodome occupies more than nine acres and seats 60,000 people.
If the stadium were a model for an atom, a marble could represent its nucleus!

31. Development of the Atomic Theory Outline Activity
HW- please work on page 1 of the Atom Worksheet and your Atomic Theory Outline/Foldable

32. Development of the Atomic Theory Timeline Activity – DAY 2
Show me your timeline!!!
Let’s review those great scientists!!

33. Comparing Dalton, JJ Thomson, and Rutherford
This is a one question quiz on youtube….

34. HISTORY OF THE ATOM Niels Bohr 1913
studied under Rutherford at the Victoria University in Manchester.
Bohr refined Rutherford's idea by adding that the electrons were in orbits. Rather like planets orbiting the sun. With each orbit only able to contain a set number of electrons.

35. Bohr’s Atom
electrons in orbits
nucleus

36. Summary
Dalton’s Theory- all matter is made up of atoms, which can’t be divided
Thomson’s Model- discovered atoms were made up of smaller particles (these smaller particles are charged)
Rutherford’s Theory- discovered the positively charged nucleus

37. Parts of an Atom Atom = nucleus surrounded by one or more electrons
Atoms are neutral (no charge)
same number of protons as electrons.
Majority of the atom is empty space.
If nucleus were the size of a pencil eraser, the closest electron would be 100 yards away!
Subatomic Particles
Protons (+)
Neutrons (0)
Electrons (-)
Nucleus: Tightly packed
Protons & Neutrons
Electrons Orbiting nucleus
@ speed of light!!

38. HELIUM ATOM + - + - Shell proton neutron electron
What do these particles consist of?

39. ATOMIC STRUCTURE
Particle
Charge
Mass
proton
+ charge 1
neutron
No charge 1
electron
- charge
nil

40. Atomic Number Atomic Number = # of Protons
Each Element in the Periodic Table has a different number of Protons, therefore each element has a different, unique, atomic number.
When reading the Periodic table notice each element has a unique 1 or 2 letter symbol and “big” & “small” number listed

41. Eureka - Electrons

42. number of electrons = number of protons
ATOMIC STRUCTURE He 2
Atomic number
the number of protons in an atom 4
Atomic mass
the number of protons and
neutrons in an atom
number of electrons = number of protons

43. Can you read these?

44. Atomic Number and Mass Activity Contents of each box
Draw a box for your chosen element from your atom project and explain in detail what each of these are!!
Atomic number
Symbol
Element name
Atomic mass

45. Electrical Atomic Charge
Remember that Atoms are neutral (no charge)
So, the # of protons = # of electrons
If you know the Atomic #, you know the # of Protons and also the # of Electrons!!
For example:
Carbon has an atomic # of 6, it therefore has 6 Protons which has an electrical charge of +6, to make the atom neutral we need 6 negative charges found in the 6 electrons orbiting the nucleus.

46. Mass number (atomic mass)
Atomic Mass = the total # of Protons & Neutrons
( we don’t worry about the mass of the electrons since they have almost no mass)

47. How many Neutrons are there?
Remember:
The Atomic # = the # of Protons
The Atomic mass = The # of both Protons & Neutrons.
Therefore, if you subtract the Atomic # (the number of Protons) from the Atomic mass (the number of both Protons & Neutrons) what is left over must be the number of Neutrons!!
For Example w/ Carbon:
Atomic Mass-Atomic # = # Neutrons
Atomic Mass = 12, Atomic # 6
12 – 6 = 6
Therefore there are 6 neutrons present in the Carbon nucleus
If you don’t believe me… just count for yourself.

48. What is an Isotope?
Atoms with the same number of protons, but a different number of neutrons.
“Same number of protons” means same atomic number, which means same element.
“Different number of neutrons” means different mass numbers.

49. Isotopes
Can sometimes be represented with dashes and numbers that follow the element.
C-14
Pu-246
O-16
O-17

50. Heavy Water
Video clip
Information about heavy water

51. Element Symbol Quiz
You need to know the element symbol for the following elements:
1-20
24-30
35,47,50,53
79,80,82,86,88
You will have a quiz on _____________
I will give you the symbol or the name and you will have to give me the other…there will be NO WORD BANK!

52. Review How many protons and neutrons are there in an atom of 115B?
A 5 protons and 6 neutrons
B 5 protons and 11 neutrons
C 11 protons and 5 neutrons
D 11 protons and 6 neutrons

53. How many neutrons are in an element of Pu-246?
B. 150
C. 152
D. 246

54. What are Oxygen-17 and Oxygen-18?
How many protons do they each have?
How many neutrons do they each have?

55. Neils Bohr, 1913
From a study of Hydrogen, concluded that an electron travels around the nucleus in circular paths called orbits
Each pathway represents an energy level.
Only orbits of certain energies are allowed. Electrons can’t exist between orbits.
Like rungs on a ladder
Bohr’s model animation

56. Niels Bohr Level closest to nucleus has lowest energy
Energy must be added for an electron to move up a level. Energy is released when an electron moves down.

57. ATOMIC STRUCTURE
Electrons are arranged in Energy Levels or Shells around the nucleus of an atom.
first shell a maximum of 2 electrons
second shell a maximum of 8 electrons
third shell a maximum of 18 electrons

58. Bohr’s Planetary Model – looks like planets orbiting the sun!!!
How many electrons are present in each orbit? 2 8 18 32

59. Electron Cloud Model – advanced from Bohr’s model
Bohr’s “orbits” are now “principal energy levels”.
Bohr was incorrect in assuming that electrons moved like planets in a solar system.
The Electron Cloud model shows the MOST LIKELY location of electrons in an atom!! (these are not precise since it’s all based on probability!!)
Think of a propeller on an airplane...you can see the blades when they aren’t moving…when it is moving you see only a blur…this is like the electron cloud model!!
The number of electrons in each principal energy level is still correct
2, 8, 18, 32
More atoms shown with Bohr’s model

60. Which of the following provides the best analogy for an electron in an atomic orbital?
a. a bee buzzing from flower to flower in a garden
b. a bird flying high in the sky
c. an ant crawling on the surface of a leaf
d. a bee buzzing inside a closed jar

61. Quantum Mechanical Model (electron cloud model)

62. Bohr Model

63. Atomic Orbitals
Orbital – a region of space around the nucleus where an electron is most likely to be found (think of a map of the school and dots that mark your location every 10 minutes)
Electron configuration – the arrangement of electrons in the orbitals of an atom
Most stable – electrons are in orbitals with the lowest possible energy

64. Remember!! When electrons move to a higher orbital they GAIN energy!!
When electrons move to a lower orbital they RELEASE energy!!

65. Structure of the Atom

66. Electron Cloud Models
Please draw electron cloud models (Bohr models) for these elements: (please make sure you show # of protons and neutrons as well!!)
Oxygen or Argon

67. Now: Assign Atom’s Project – put a Bohr Model in your composition book
Work on Atomic Mass worksheet
Work on Atom’s worksheet
Take notes on Periodic Table
Elementary My Dear Watson

68. History of Atomic Structure Video clip