BIOL 111 Chapter Notes - Chapter 2: Unified Atomic Mass Unit, Atomic Nucleus, Chemical Formula
23 Dec 2019
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Concept 2. 1: matter consists of chemical elements in compounds and pure form. Organisms are composed of matter = anything that takes up space and has mass: can be organic or inorganic, anything that takes up space. An element is a substance that cannot be broken down into other substances by chemical reactions. A compound is a substance consisting of two or more elements. Compounds have characteristics different from those of their constituent elements: ex. sodium + chlorine sodium chloride (table salt) Most of our mass = just 4 elements. About 20-25% of the 92 elements are essential to life. Carbon, hydrogen, oxygen, and nitrogen make up 96% of living matter. Trace elements are those required by an organism in minute quantities: show up in very small quantities, ex. magnesium. The human body - lots of o c h n. Concept 2. 2: an element"s properties depend on the structure of its atoms.
