3.1 Atomic Theory and Atomic Structure
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Atomic Theory
| MODERN ATOMIC THEORY |
|---|
| 1. All matter is composed of atoms. |
| 2. The atoms of an element are identical but different than atoms of other elements. |
| 3. The atoms of one element cannot be converted to another element by chemical reactions. |
| 4. Compounds are formed when atoms of different elements combine in whole number ratios. |
Atomic Structure
Atomic Structure - An atom is comprised of a nucleus at its center that is composed of protons and neutrons surrounded by an electron cloud.
| ATOMIC THEORY SCIENTISTS | |
|---|---|
| Dalton | Proposed his atomic theory |
| Thompson | Discovered electrons |
| Millikan | Determined the charge of an electron (oil drop experiment) |
| Rutherford | Discovered the nucleus (scattering of alpha particles in thin gold foil) |
Isotope Symbols
| ISOTOPE SYMBOLS |
|---|
| Atomic Number – Equals the number of protons |
| Mass Number – Equals the sum of the number of protons plus neutrons |
| Charge – Equals the number of protons minus the number of electrons |
| Isotopes – Forms of elements that have different mass numbers due to differing numbers of neutrons |
Atomic Weight (a.k.a. Atomic Mass)
| Isotope | Mass | Abundance |
|---|---|---|
| 35Cl | 34.97a.m.u. | 75.8% |
| 37Cl | 36.97a.m.u. | 24.2% |
What is the atomic mass (also called atomic weight) of chlorine?