1. ATOMIC STRUCTURE
S.MORRIS 2006

2. (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)

3. 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

4. Dalton’s Atomic Theory
All matter is composed of tiny particles called atoms.
Atoms of the same element are identical in size, mass, and chemical properties. (*Has been disproved*)
Atoms cannot be subdivided, created, or destroyed. (*Also disproved*)
Atoms of different elements combine in simple whole-number ratios to form chemical compounds.
In chemical reactions, atoms are combined, separated, or rearranged.

5. HISTORY OF THE ATOM Joseph John Thompson
1898
Discovered the negtatively (-) chargered ELECTRON using a Cathode Ray Tube.
Particles were attracted to (+) positively charged plates.
What do we know about opposites??

6. Thompson’s Cathode Ray Tube

7. 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

8. HISTORY OF THE ATOM Ernest Rutherford
1910
Ernest Rutherford
For his famous experiment he fired Helium nuclei at a piece of gold (Au) foil which was only a few atoms thick.
He found that although most of the nuclei passed right through, about 1 in 10,000 hit something??

9. HISTORY OF THE ATOM
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.

10. HISTORY OF THE ATOM
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.

11. HISTORY OF THE ATOM Niels Bohr
1913
Niels Bohr
He studied under Rutherford at the Victoria University in Manchester.
Bohr refined Rutherford's idea by adding that the electrons were in orbits called energy levels. Rather like planets orbiting the sun. Each energy level is only able to contain a set number of electrons.

12. Which Atom Model belongs to which Scientist?

13. Niels Bohr’s Work with Hydrogen Gas
Bohr found that when electrons are excited they absorb energy and jump from their Ground State to a higher energy level.
When they fall back down from this Excited State they give off energy in the form of Photons of light.
Each energy level gives off its own color of light creating a Line Spectrum.

15. The Electromagnetic Spectrum
There is an inverse relationship between Wavelength, Frequency, and Energy.
The GREATER the Energy and Frequency the shorter the Wavelength.
Visible light is a very small part of the EM Spectrum
Violet has the smallest wavelength, highest energy, and highest frequency of the visible spectrum.
Which color has the longest wavelength, lowest frequency, and lowest energy?

16. Dangers of Electromagnetic Radiation
The least dangerous is Radio Waves
The MOST dangerous is Gamma Waves

17. Wavelength (λ), Frequency (f) and
Energy (E)
Speed of Light Constant
c = 3.0 x 108m/s
Planks Constant
h = x 10-34 J s

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

19. Number of protons = Number of electrons
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 protons = Number of electrons

25. 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 in a neutral atom.
Electrons orbit the nucleus in energy levels (shells).
Each energy level can only carry a set number of electrons.