BIOL 1201 Chapter : Biology Chapter 2
Document Summary
Matter consists of chemical elements in pure form and in combinations called compounds. Organisms are composed of matter, which is anything that takes up space and has mass. An element is a substance that cannot be broken down to other substances by chemical reactions. 4 elements make up about 96% of living matter: carbon, hydrogen, Trace elements are those required in only very small quantities in an organism. An elements properties depend on the structure of its atoms. An atom is the smallest unit of matter that still retains the properties of an element. Composed of even smaller units of matter called subatomic particles. Protons and neutrons are packed together tightly in the nucleus at the center of an atom. Electrons exist in a cloud of negative charge surrounding the nucleus. The attraction between opposing charges keeps the electrons in the vicinity of the nucleus. (fig 2. 5)
