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Ch. 18 Science
| Term | Definition |
|---|---|
| Element | Any pure substance that is made of only one kind of atom |
| Aristotle believed in 4 "elements"... | Air, Fire, Earth, Water |
| Alchemy | Includes aspects of chemistry, philosophy, religion, metallurgy, medicine, and art |
| Isaac Newton, Robert Boyle, and Antoine Lavoisier | believed that true scientific knowledge was gained by observing, experimenting, and reasoning. |
| Number of elements today | 117 |
| Number of naturally occurring elements | 92 |
| Number of solids at room temperature | 13 |
| Number of liquids | 2 (Hg and Br) |
| Number of gases | 11 (H, He, N, O2, F, Ne, Cl, Ar, Kr, Xe, Rn) |
| Monotomic Elements | 1 atom in their natural state (He, Ne, Ar, Kr, Xe, Rn) |
| Diatomic Elements | 2 atoms in the natural state (H2, N2, O2, F2, Cl2, Br2, I2) |
| Dmitri Mendeleev | arranged the elements into what eventually became the periodic table used today |
| Johann Dobereiner | placed the elements in order of increasing mass. Almost all groups contained 3 elements so he called them triads |
| Periodicity | the repetition of certain properties at regular intervals when elements were placed in order of atomic mass |
| John Newlands | arranged the elements in the able in order of their increasing atomic masses. when arranged in seven columns he noted that in most cases every 8th element had similar properties. He called these octaves. |
| Dmitri Mendeleev | arranged the cards until he had grouped similar elements in rows. He included blank spots for undiscovered elements. |
| Periodic Law | the principle that the properties of elements vary in a periodic or recurring pattern with their atomic masses |
| Henry Moseley | discovered how to use X-rays to count the protons in an atom's nucleus to find an element's atomic number. Arranged in order of increasing atomic number. |
| Metals | Luster, Malleable, Conduct electricity, Ductile |
| Non-Metals | Lack luster, brittle, Don't conduct electricity, Not ductile |
| Periods/Series | horizontal rows of the periodic table |
| Period number | tells how many main energy levels the elements in that period have in their ground state |
| Ground State | lowest energy state for the electrons |
| Lewis Dot Notation | illustrates the arrangement of valence electrons in an atom |
| Second Law of Thermodynamics | governs the tendency for atoms to form bonds; states that all natural processes move toward a state of minimum energy |
| Octet Rule | atoms are generally most stable when they have a full 8 electrons in their valence energy level. Atoms can gain, lose, or share electrons to get to the octet. |
| Electron Affinity | deals with the strength of attraction of electrons to unbonded atoms. High affinities will take or share electrons from other atoms. Low affinities will lose their valence electrons or have a very small part in sharing them when bonding. |
| Electronegativity | deals with an atom's ability to attract and hold electrons when bonded to other atoms. the more electronegative the more likely it will take electrons |
| Covalent bonds | non-metal/non-metal...sharing electrons |
| Ionic bonds | metal/non-metal...giving away and taking electrons |
| Metallic bonds | metal/metal...every shares the electrons |
| Electron Sea Theory | Atoms with weak electronegativity usually have only a few loosely held valence electrons. These atoms bond by sharing their easily lost electrons among many atoms. These mobile electrons are not associated with any specific nucleus. |
Created by:
akdodd
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