1. Atomic Structure Notes

2. History of the Atom 1808 John Dalton 1897 Joseph Thomson
Matter made of tiny particles called atoms
1897 Joseph Thomson
Discovery of electrons using cathode rays
1909 Robert Millikan
Discovery of negative charge on electrons
1911 Ernest Rutherford
Discovery of nucleus, lots of open space in an atom
1914 Neils Bohr
Electrons orbit the nucleus in different shells
Modern Atomic Theory

3. Atom –
The smallest particle of an element that retains the chemical properties of that element.
Nucleus –
Positively charged center of the atom that consisting of protons and neutrons that contain nearly all the atoms mass with a very low volume.

4. Proton –
Subatomic particle of the nucleus that has a positive charge.
Neutron –
Subatomic particle of the nucleus that has a neutral charge.
Electron –
Subatomic particle outside the nucleus that has a negative charge.

5. Proton
Neutron
Nucleus + N N +
Electron -
Electron Region

6. Subatomic Particles
Name
Charge
Weight
Proton +
1 amu
Neutron N
Electron -
.0005 amu

7. Atomic Mass Unit –
1 amu, exactly 1/12 the mass of a carbon-12 atom.
Average Atomic Mass –
The weighted average of the atomic masses of the naturally occurring isotopes of an element.
Isotopes –
Atoms of the same element that have different masses.

8. Atomic Number –
The number of protons in the nucleus of each atom of that element. Used to identify elements.
Mass Number –
The total number of protons and neutrons in the nucleus of an atom.
Mass # = Protons + Neutrons
Neutrons = Mass # - Protons

9. Mass Number, Protons, Neutrons and Electrons
Element
Protons
Neutrons
Electrons
Mass #
Hydrogen 1
Carbon-12 6 12
Carbon-14 8 14
Oxygen-16 16
Oxygen-17 9 17

10. Hyphenated Notation
Carbon – 14
Element Mass #

11. Atomic Number and Mass Notation14 6
Mass # Atomic # Symbol C

12. Relation of atomic mass and molar mass
Carbon-12
Atomic mass = amu
Molar mass = g/mol
The only difference is the units 