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chap 17-18 ps
| Term | Definition |
|---|---|
| element | pure substance |
| aristotle | believed in air fire earth water |
| element # how many? | 117 |
| naturally occuring elements | 92 |
| johann Dobereiner | triads |
| periodicity | repition of certain properties at periodic intervals when elements are placed in order of atomic mass |
| John Newlands | aranged table in order of atomic mass every eight had similar props: OCTAVES |
| Dmitri Mendelev | in order of atomic mass left blanks for undiscovered elements credited for modern pecha |
| Henry Moseley | counted protons w/ x-rays rearanged pecha into modern one and revised periodic law |
| periodic law (modern changed from atomic mass to _____) | The properties of elements vary in a periodic way with their atomic number |
| 2nd law of thermodynamics | all natural processes move toward a state of minimum energy |
| atoms are most stable with 8 valence electrons | octet rule |
| covalent | sharing electrons non metal with non metal high melting temp |
| ionic | low melting temp produce electricity when dissolved in water metal/nonmetal give away and take electrons |
| mettalic | metal/metal |
| electron sea | electrons bounce everywhere |
| electron affinity | strength of attraction to UNBONDED atoms |
| electronegativity | how powefully it can take electrons when bonded (flourine highest) |