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Atomic Theory
Scientists and Atomic models
| Term | Definition |
|---|---|
| Atom | The smallest unit of an element that maintains (keeps) the properties of that element. |
| Electron | A negatively charged subatomic particle OUTSIDE the nucleus of an atom. |
| Nucleus | In physical science, an atom's central region. |
| Proton | A subatomic particle that has a POSITIVE charge and that is located INSIDE the nucleus. |
| Neutron | A subatomic particle that has a NO CHARGE and that is located INSIDE the nucleus. |
| Electron Cloud | An area around the nucleus where electrons are in motion. |
| Atomic Number | The number of protons (and electrons) in an atom. The atomic number is the same for all atoms of that element. |
| Mass Number (Atomic Mass) | The sum of the numbers of protons and neutrons in the nucleus of an atom. |
| Isotope | One of 2 or more atoms that have the same number of protons (atomic number) but different numbers of neutrons (atomic mass) |
| JJ Thomson | Individual atoms were thought of as positively charged SPHERES with negatively charged electrons EMBEDDED (stuck) in it. Plum Pudding |
| Niels Bohr | Explained that electrons were moving in FIXED SHELLS around the nucleus. |
| John Dalton | British school teacher that proposed the first atomic theory. |
| Ernest Rutherford | Individual atoms were positively charged spheres with negative electrons ORBITING the center. The atom is MOSTLY EMPTY SPACE. |
| Modern Model | The atom has a positively charged nucleus and a negatively charged CLOUD of electrons. |