BIOL 1201 Chapter : Ch 2
Document Summary
Matter: anything that takes up space and has mass (rocks, metals, oils, humans) Element: a substance that cannot be broken down to other substances by chemical reactions (92 in nature: each has a symbol) Compound: substance consisting of 2 or more different elements combined in a fixed ratio (table salt: sodium chloride (nacl)) Essential elements: organism needs to live a healthy life & reproduce. Trace elements: required by an organism in only minute quantities. Atom: the smallest unit of matter that still retains the properties of an element. Subatomic particles: tiny bits of matter composed of smaller part. Atomic nucleus: dense core, at the center of the atom. Dalton: unit of measurement in honor of john dalton, british scientist who helped develop atomic theory. Atomic number: number of protons in their nuclei (written as a subscript to the left of symbol) Mass number: sum of protons plus neutrons (superscript to the left)
