1. ATOMIC STRUCTURE
S.MORRIS 2006

2. Papercuts This piece of paper is 28cm x 2.5 cm
How many times can you cut the piece of paper in half?
Once you cut a piece in half, you have to discard one half and then use the other piece to continue this process
Repeat this until you can no longer cut the paper.
How many cuts did you make?

3. Width of an Atom The average width of an atom is 130 picometers
1pm = m = 1/ of a meter
 1 millimeter = 1 000 000 000 picometers
That’s teeny tiny !

4. Who are these dead dudes?
How did they contribute to our present day model of an atom?

5. (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 he called
ATOMA
(greek for indivisible)

6. This theory was ignored and forgotten for more than 2000 years!

7. 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

8. Dalton’s Theory Dalton’s Atom all elements are composed of atoms.
atoms of the same element are exactly alike.
atoms of different elements are different.
compounds are formed by the joining of atoms of two or more elements.
Fill this in on your Notes sheet
Dalton’s Atom

9. 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

10. 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

11. 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

12. 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.

13. 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.

14. 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.

15. Bohr’s Atomic Theory
The Bohr model was a modification of the Rutherford model.
Bohr the electrons in certain circular orbits around the nucleus called shells. +

16. Scientists had learned a lot about the atom, but couldn’t figure out what made it so heavy. In 1932 James Chadwick solved the mystery by coming up with the idea of neutrons, neutral particles that live in the nucleus with protons. The new improved Bohr model includes these particles.
Neutrons

17. Bohr Model of a HELIUM ATOM
New Bohr Model
Bohr Model of a HELIUM ATOM
Shell
proton N + - + N -
neutron
electron

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

19. He 2 4 Use your periodic table to help you find the ATOMIC STRUCTURE
Atomic number
the number of protons in an atom 4
Atomic mass
the number of protons and
neutrons in an atom
Charge = # of protons + # of electrons
= (+ number) + (- number)
If the number of protons is the same as the number of electrons, what is the charge of the atom?

20. 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

21. Nucleus 1st shell 2nd shell 3rd shell
Adapted from

22. Created by G.Baker www.thesciencequeen.net
So let’s try it….
How to draw a Lithium atom
First, look at the Periodic Table
Second, How do you find the number of protons?
Then determine the number of neutrons
Then determine the number of electrons 3 Li
Lithium 7
Created by G.Baker

23. Created by G.Baker www.thesciencequeen.net
So let’s try it….
Protons = 3 3 Li
Lithium 7 - + + + - -
Electrons = 3
2 in the 1st shell, 1 in the 2nd shell
Neutrons = 4
(7-3=4)
Created by G.Baker