BIOL 110 Lecture Notes - Lecture 2: Unified Atomic Mass Unit, Iodine, Sulfur
8 Sep 2016
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Document Summary
Matter consists of chemical elements in pure form and in combinations called compounds: Element- a substance that can not be broken down to other substances by chemical reactions; purest form of matter. Compound- a substance consisting of two or more elements is a fixed ratio; has characteristics different from those of its element. About 25 of the 92 elements are essential to life. Carbon, hydrogen, oxygen, and nitrogen make up 96% of living matter. The remaining 4% consists of calcium, phosphorous, potassium, and sulfur. Trace elements are those required by an organism in minute quantities. An element"s properties depend on the structure of its atoms. Atom- an atom is the smallest unit of matter that still retains the properties of an element. Electrons- negative charge; found in the orbital 90% of the time. Neutron mass and proton mass are almost identical and are measured in daltons. Atomic number- is the number of protons in the nucleus.
