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Unformatted text preview: Chapter 2 : Rocks and Minerals – A First Look Elements, Isotopes, and Ions : Nucleus – At the center of the atom and contains one or more particles with a + (positive) electrical charge ( protons ) and usually some particles of similar mass that have no charge ( neutrons ). Circling the nucleus are the – (negatively) charged electrons . Atomic #- The characteristic # of protons on an atom of the element. (Every hydrogen atom contains 1 proton in its nucleus; every Oxygen atom contains 8 protons in its nucleus; every carbon aton has 6 protons; every iron atom has 26 protons, and so on.) Atomic Mass #- The sum of the # of protons and the # of neutrons in a nucleus of an atom. Isotopes – Atoms with the same # of protons, but a different # of neutrons, distinct from the “periodic table” element are isotopes of that element. Ion – In an electrically charged neutral atom, the # of protons and the # of electrons are the same. (The negative charge of one electron just = the positive charge of one proton.) Most atoms can however gain or lose some electrons. When this happens, the atom has a distinct positive or negative charge, and is called an Ion . • If it loses electrons, it becomes positively charged (called a cation ), since the # of protons then exceeds the # of electrons. • If it gains an electron, the atom has a negative electrical charge and is called a ( anion ). Minerals : Minerals – Naturally occurring, inorganic, solid element or compound, with a definite chemical composition and a regular internal crystal structure. • Naturally occurring as distinct from synthetic, means that materials do not include the thousands of chemical substances invented by humans. • Inorganic , in this context, means not produced solely by living organisms or by biological processes. • Solid means that the ice of a glacier is a mineral, but liquid water is not.- Chemically, minerals consist either of one element (such as diamonds, which are pure carbon), or they may be compounds of two or more elements. (Some mineral compositions are very complex, consisting of 10 elements or more.) • Minerals have a definite chemical composition or compositional range within which they fall. The presence of certain elements in certain proportions is one of the identifying characteristics of each mineral.- Minerals are crystalline , at least on the microscopic scale. Crystalline – (Crystalline materials) are solids in which the atoms are arranged in regular, repeating patterns. (These patterns may not be recognizable by the naked eye, but most solid compounds are crystalline, and their crystal structures can be recognized and studied using X rays and other techniques.) Identifying Characteristics of Minerals- Two fundamental characteristics of a mineral that together distinguish it from all other minerals are: • Its chemical composition • Its crystal structure No two minerals are identical in both respects, though they may be the same in one....
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- Fall '08
- Sedimentary rocks, Clastic Sedimentary Rocks Chemical Sedimentary Rocks