1. ATOMIC STRUCTURE More free powerpoints at www.worldofteaching.com
S.MORRIS 2006

2. ~ The Hellenic Market Fire Water Earth Air
Original concept of element:
Four element theory
AIR combined to form all other materials by combining
WATER in different proportions.
EARTH
AIR
Fire Water Earth Air ~

3. The Greeks History of the Atom
Not the history of atom, but the idea of the atom
In 400 B.C the Greeks tried to understand matter (chemicals) and broke them down into earth, wind, fire, and air. ~ ~

4. (greek for indivisible)
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 he called
ATOMA
(greek for indivisible)
No experiments to support idea
Continuous vs. discontinuous theory of matter
Democritus’s model of atom
No protons, electrons, or neutrons
Solid and INDESTRUCTABLE

5. Four Element Theory Plato was an atomist
Thought all matter was composed of 4 elements:
Earth (cool, heavy)
Water (wet)
Fire (hot)
Air (light)
Ether (close to heaven)
‘MATTER’
FIRE
EARTH
AIR
WATER
Hot
Wet
Cold
Dry
THE SCEPTICAL CHYMIST (1661)
“The Greeks believed that earth, air, fire, and water were the fundamental elements that made up everything else. Writing in 1661, Robert Boyle ( ) argued against this idea, paving the way for modern ideas of the elements. He defined an element accurately as a substance that could not be broken down into simpler substances.”
Eyewitness Science “Chemistry” , Dr. Ann Newmark, DK Publishing, Inc., 1993, pg 18
Plato was Aristotle's student. It was Aristotle that suggested qualities of "hot, dry. cold, wet".
Aristotle
Added the idea of “qualities” –
heat, cold, dryness, moisture
Hot + dry made fire; hot + wet made air, and so on.
Blend these “elements” in different proportions to get all substances

6. Who Was Right? Greek society was slave based
Beneath famous to work with hands
did not experiment
Greeks settled disagreements by argument
Aristotle was more famous
He won!
His ideas carried through middle ages.
Alchemists change lead to gold
California WEB

7. Alchemy After that chemistry was ruled by alchemy.
They believed that that could take any cheap metals and turn them into gold.
Alchemists were almost like magicians.
elixirs, physical immortality

8. Contributions of alchemists: Information about elements
- the elements mercury, sulfur, and antimony were discovered
- properties of some elements
Develop lab apparatus / procedures / experimental techniques
- alchemists learned how to prepare acids.
- developed several alloys
- new glassware

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

11. 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

12. 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

13. 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.

14. 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.

15. 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.

16. Bohr’s Atom
electrons in orbits
nucleus

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

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

19. 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

20. Complete the following table in your notes
Atomic #
Mass #
# of Protons
# of Neutrons
# of Electrons 9 10 14 15 47 22 55 25

21. “POP QUIZ”! Define the following terms on a separate sheet of paper
Atomic number
Ion
Molecule
Atom
Valence Electrons

22. How’d You Do?
The number of protons in the nucleus of an atom of an element
An atom or group of atoms that has a positive or negative charge due to a gain or loss of electrons
A neutral chemically bonded group of atoms that act as a unit
The smallest particle of an element that retains the properties of that element
An electron that is in the highest energy level

23. Isotopes
Atoms that have the same number of protons but different numbers of neutrons
Different mass numbers
Chemically alike because they have identical numbers for the characteristic chemical behavior of each element
Ex: Three known isotopes for H
Hydrogen (no neutrons, mass # of 1)
Deuterium (one neutron, mass # of 2)
Tritium (two neutrons, mass # of 3)

24. Your turn…
Two of the isotopes for Carbon are Carbon-12 and Carbon-13, write the chemical symbol for both
126C
136C
Three isotopes for Oxygen are oxygen-16, oxygen-17, and oxygen-18, write the chemical symbol for all three
168O
178O
188O

25. Calculating Average Atomic Mass of Isotopes
In nature, isotopes occur in various percentages
In order to figure out the average mass of each element the percent abundance and mass of each isotope need to be considered
We can calculate average atomic mass in much the same way as we calculate your grade in this class…

26. What are the different categories that you are graded on in this class?
Classwork: 79%
Practice: 7%
Final: 14%
What would your semester grade be if you received an 80% for classwork, 50% for practice, and 72% on your final?
0.80 x 79 = 63.2
0.50 x 7 = 3.5
0.72 x 14 = 10.1
Add all answers together to get % semester grade:
= 76.8 % (a C)

27. Now lets try with an element!
Copper has two isotopes: copper-63 and copper-65. The relative abundances of these isotopes are 69.2% and 30.8% respectively. Calculate the average atomic mass of copper.
0.692 x 63 = 43.60
0.308 x 65 = 20.02
= 63.62

28. One more example…
Uranium has three naturally occurring isotopes with the following percent abundances: U-234 (0.0058%), U-235 (0.71%), and U-238 (99.23%).
What do you expect the average atomic mass to be and why?
What is the average atomic mass?
237.85

29. 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 8 electrons

30. SUMMARY The Atomic Number of an atom = number of
protons in the nucleus.
The Atomic Mass of an atom = number of
Protons + Neutrons in the nucleus.
The number of Protons = Number of Electrons.
Electrons orbit the nucleus in shells.
Each shell can only carry a set number of electrons.

31. 1. Electronic Configuration
ATOMIC STRUCTURE
There are two ways to represent the atomic structure of an element or compound;
1. Electronic Configuration
2. Dot & Cross Diagrams

32. ELECTRONIC CONFIGURATION
With electronic configuration elements are represented numerically by the number of electrons in their shells and number of shells. For example;
Nitrogen
configuration = 2 , 5 7
2 in 1st shell
5 in 2nd shell N
= 7 14

33. ELECTRONIC CONFIGURATION
Write the electronic configuration for the following elements; 20 11 8 Na O Ca a) b) c) 16 23 40
2,8,8,2
2,8,1
2,6 17 14 5 Cl Si B d) e) f) 11 35 28
2,8,7
2,8,4
2,3

34. N DOT & CROSS DIAGRAMS Nitrogen
With Dot & Cross diagrams elements and compounds are represented by Dots or Crosses to show electrons, and circles to show the shells. For example; X
Nitrogen N 7 X X N X X 14 X X

35. DOT & CROSS DIAGRAMS O Cl
Draw the Dot & Cross diagrams for the following elements; X 8 17 O Cl a) b) X 35 X 16 X X X X X Cl X X X X X X X O X X X X X X X X X X