BSC 2010C- Midterm Exam Guide - Comprehensive Notes for the exam ( 18 pages long!)
Document Summary
Elements- can"t be broken down by simple chemical reactions. Of the 92 elements about 20%-25% are essential elements. Trace elements- required by an organism in only minute quantities. Compound- a substance consisting of two or more different elements combined in a fixed ratio (example: nacl) Atom- smallest unit of matter retaining properties of a given element. Represents the # of electrons in neutral atoms. Atoms of different elements differ in the number of subatomic particles. Atomic nucleus- center of an atoms, consist of protons & neutrons packed tightly together. Rapid movement of electrons form a cloud of negative charge around the nucleus. Only electrons are directly involved in chemical reactions. John dalton, british scientist who helped develop the atomic theory. Dalton is the same as the atomic mass unit, or amu. Neutrons & protons have masses close to 1 dalton. Know the mass # and atomic #, you can figure out the neutron #
