BIOL 151 Study Guide - Electron Shell, Radiocarbon Dating, Covalent Bond
Document Summary
All life is composed of matter: it"s the stuff . Element= any substance that cannot be broken down into other substances by chemical reactions. There are 92 naturally occurring elements; 25 are essential to life. Water is 96% of body, carbon 18. 5%, hydrogen 9. 5%, nitrogen 3%, 4% other elements. Trace elements= element requires in very tiny quantities, but indispensable (crucial) for life. Deficiency of trace elements results in abnormal functioning of organs, glands, etc. May prevent essential life processes from occurring. Molecule: 2 or more atoms held together (ex: o2, co) (covalent) Compound: substance composes of 2 or more different atoms in fixed ratio (ionic) Organic compounds: compounds synthesized by cell and containing carbon (c) Nucleus contains protons & neutrons, and the electrons orbit around the core. Atomic mass: protons + neutrons, bc electrons don"t have much mass relative to a p & n. electrons don"t really get factored in the mass. Neutrons contribute to the mass of an atom.
