1. The Atom

2. Law of Conservation of Mass
Was discovered by Antoine Lavoisier
Helped moved alchemy to be chemistry
Mass cannot be created nor destroyed in normal chemical or physical processes.

3. Aristotle – the four basic elements
-Earth
-Air
-Water
-Fire

4. Democritus
Follower of Leucippus
An Atomist
Coined the word atomos meaning uncuttable or the smallest particle of matter

5. 2000 years later John Dalton – School Teacher
Five main points of Dalton's atomic theory
Elements are made of tiny particles called atoms.
All atoms of a given element are identical.

6. 3. The atoms of a given element are different from those of any other element; the atoms of different elements can be distinguished from one another by their respective relative atomic weights.
4. Atoms of one element can combine with atoms of other elements to form chemical compounds; a given compound always has the same relative numbers of types of atoms.
5. Atoms cannot be created, divided into smaller particles, nor destroyed in the chemical process; a chemical reaction simply changes the way atoms are grouped together.

7. Daltons Model of the Atom

8. Cathode Ray Tube

9. Plum Pudding Model of the Atom
JJ Thompson

10. Gold Foil Experiment – Ernest Rutherford

11. Rutherford’s Model of the Atom

12. Particle
Symbol
Relative Charge
Mass (kg)
Mass Number
Location
electron e- -1
9.109x10-31
Around Nucleus
proton p+ +1
1.673x10-27 1
Nucleus
neutron n0
1.675x10-27

13. Atomic Number: The number of protons in the nucleus of an atom
Mass Number: The total number of protons and neutrons on a nucleus
Atomic Number
Symbol
Atomic Mass

14. Isotope: Atoms of the same element that have different masses

15. Determining the number of protons neutrons and electrons in an isotope.
# of protons = atomic number 17
# of neutrons = mass number – atomic number
= 18
# of electrons = # of protons in a neutral atom 35 17 Cl
# of protons = atomic number 35
# of neutrons = mass number – atomic number
80 – 35 = 45
# of electrons = # of protons in a neutral atom
Bromine-80

16. Practice!! Aluminum -27 Copper-65 B Xe Lead-208
protons-13 neutrons-14 electrons-13
protons-29 neutrons-36 electrons-29
protons-5 neutrons-6 electrons-5
protons-54 neutrons-77 electrons-54
protons-82 neutrons-126 electrons-82 11 5
131 54