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Chemistry Unit 1
| Term | Definition |
|---|---|
| Atom | Smallest particle of an element that retains all the properties of that element |
| Democrtius(400 Bc) | All mater is made of tiny indivisible particles called atomos=indivisible. Philosopher not a scientist |
| John Dalton (1803) | Thought atoms looked like tiny marbles. Did not know about protons, neutrons, and electrons(subatomic particles) |
| Atomic Theory Of Matter | 1. Elements are made of tiny, indivisible particles(not true). @. All atoms of a given element are identical. 3. Atoms can't be created or destroyed. 4. Compounds are formed from combining different elements |
| J.J Thomson (1896) | Discovered electrons and conducted Cathorode Ray Tube Eperiment and created Plum pudding model |
| Cathorode Ray Tube Experiment | 1. Particles deflected towards positive plate 2. AToms contain negative charged particles |
| Gold Foil Experiment | Experiment by Rutherforf where beams of positive alpha particles were fired through gold Foil and some were deflected so he concluded that atoms are mostly empty with a small positive nucleus |
| Planetary Model | Created by Niels Bohr and atoms had a nucleus with electrons found in orbit |
| Quantum (Wave) Mechanical Model | 1. AToms have a dense, positive nucleus 2.Electrons with distinct amounts of energy travel in orbitals 3, Electrons can act as particles and waves 4. Orbital:Region where an electron of a particular amount of energy is found. |
| Atomic number | Same as the number of protons which determine what an element is and number of electrons in neutral atoms. |
| Mass Number (#of protons + neutrons) | If not given specifically than look up atomic mass on Periodic Table and round to the nearest whole number |
| # of neutrons | Mass number - Atomic number |
| Isotopes | AToms of the same element with different number of neutrons and mass number. Protons and atomic number don't change |
| Atomic Mass | Weighted average of all naturally occurring isotopes of a sample of that element |
| Electron locations | found in orbitals and gain or lose energy depending on distance from the nucleus |
| Electron Configurations | Distribution of electrons with up to 4 energy levels (2(n). |
| Valence electrons | Outermost electrons in the orbital that are the furthest from the nucleus. Look at the last number in the electron configuration |
| Ground State | All electrons are found in the lowest available energy levels closest to the nucleus. Configuration found in PT and is stable |
| Excited State | Electrons move from lower to higher energy levels away from the nucleus as atoms abosorb energy. Electrons are usnatble and release same energy that was absorbed as light as they move back. Configuration has same # of electrons with at least one higher |
| Bright Line Spectra | When light from an element is passed through a prism and ts components separated, lines in the bisivle region appear. Each atom has its own pattern that can be used to identify them and are considered an elements fingerprint |
| Ion | Atom with a positive or negative charged due to a loss or gain of elctrons, Protons and electrons are not equal |
| Anion | Atoms become negative and gain electrons |
| Cation | Atoms become positive and lose electrons |
| Atomic Mass Formula | Mass number x percentage/100 |
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