Atoms, Electrons, and the Periodic Law
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Created by:
kmazzarella on October 3, 2011
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36 terms
Terms | Definitions |
|---|---|
 Periods | 7 horizontal rows |
| Groups/Families | vertical columns of the periodic table |
| Alkali Metals | Group 1, 1 electron in outer level, very reactive, soft, silver, shiny, low density; Lithium, Sodium, Potassium, Rubidium, Cesium, Francium |
| Alkali Earth Metals | Group 2, 2 electron in the outer energy level, very reactive but less reactive than alkali metals, silver, higher densities than alkali metals; Beryllium, Magnesium, Calcium, Strontium, Barium, Radium |
| Transition Metals | Groups 3-12, 1-2 electrons in the outer energy level, less reactive than alkali-earth metals, shiny, good conductor of thermal energy and electrical current, high density |
| Halogens | group 17; contains nonmetals; 7 electrons in its outermost energy level; very reactive; poor conductors of electric current; never in its uncombined form in nature; combine with most metals to form salts |
| Noble Gases | one of the elements of group 18 of the periodic table(helium, neon,argon, krypton, xenon, and radon); noble gases are unreactive |
| Lanthanide Series | the rare-earth elements with atomic numbers 57 through 71 (top of bottom block) |
| Actinide Series | a series of 15 radioactive elements with increasing atomic numbers from actinium to lawrencium (bottom of bottom block) |
| Metals | left of the staircase, shiny, malleable, ductile, good conductors of electric current, good conductors of thermal energy |
| Nonmetals | right of the staircase, not malleable/ductile, not shiny, poor conductors |
| Metalloids | semiconductors, border the staircase, shiny, brittle, hard, at high temp- good conductors of electric current |
| Law of Mass Conservation | Matter is neither created nor destroyed during a chemical reaction |
| Law of Definite/Constant Composition | a pure compound, whatever its source, always contains definite or constant proportions of the elements by mass |
| Law of Multiple Proportions | if two or more different compounds are composed of the same two elements, then the ratio of the masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers |
| Dalton's Atomic Theory | 1) elements are composed of atoms. 2) atoms of same element are identical, but differ from other elements. 3) elements can mix together 4) atoms only change when mixed with other elements ; a theory proposed by John Dalton in 1808, based on numerous scientific experiments, that marked the beginning of the development of modern atomic theory |
| John Dalton | developed modern atomic theory |
| Protons | The total number of these determines the atomic number; these are positively charged and found in the nucleus |
| Electrons | negatively charged particles found outside the nucleus |
| Neutrons | These have no electrical charge, but add to the mass of the atom |
| Mass Number | the total number of protons and neutrons in the nucleus of an atom |
| Atomic Mass | the weighted average of the masses of the isotopes of an element |
| Isotopes | atoms of the same element that differ in the number of neutrons they contain |
| Valence Shell | The outermost energy shell of an atom, containing the valence electrons involved in the chemical reactions of that atom. |
| Ion | a particle that is electrically charged (positive or negative) |
| Homogeneous Mixture | a mixture in which the composition is uniform throughout |
| Heterogeneous Mixture | A mixture in which different materials can be distinguished easily |
| Element | any of the more than 100 known substances (of which 92 occur naturally) that cannot be separated into simpler substances and that singly or in combination constitute all matter |
| Compound | (chemistry) a substance formed by chemical union of two or more elements or ingredients in definite proportion by weight |
| J.J. Thomson | discovered electron; cathode ray tube; plum pudding model |
| Robert Millikan | discovered the charge (negative) and mass of of the electron |
| Ernest Rutherford | from his gold foil expirments, he knew some substances give off + charged particles called alpha particles, most of the mass of an atom is in the nucleus, he reasoned that electrons in the atom are whirled around outside the nucleus, most of the atom is empty space |
| Neils Bohr | Created planetary (Bohr) model of the atom |
| Dmitri Mendeleev | Russian chemist who developed a periodic table of the chemical elements by using ATOMIC MASS and predicted the discovery of several new elements (1834-1907) |
| Henry Mosley | British scientist who arranged the perodic table by atomic number |
| Atomic Mass Unit | unit of mass for expressing masses of atoms or molecules |
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