BIOL 1107 Chapter Notes - Chapter 2: Unified Atomic Mass Unit, Ionic Bonding, Chemical Formula
Document Summary
Living organisms and their environments are subject to basic laws of physics and chemistry. Matter consists of chemical elements in pure form and in combinations called compounds. A compound is a substance consisting of two or more elements in a fixed ratio. A compound has characteristics different from those of its elements. About 20 25% of the 92 elements are essential to life (essential elements) Carbon, hydrogen, oxygen, and nitrogen make up 96% of living matter. Most of the remaining 4% consists of calcium, phosphorus, potassium, and sulfur. An element"s properties depend on the structure of its atoms. An atom is the smallest unit of matter that still retains the properties of an element. Relevant subatomic particles include: neutrons (no electrical charge, protons (positive charge, electrons (negative charge, atomic nucleus, neutron mass and proton mass are almost identical and are measured in daltons. Atoms of the various elements differ in number of subatomic particles.
