BIOL 1F90 Lecture Notes - Lecture 1: Atomic Nucleus, Atomic Mass, Atomic Number
27 Sep 2017
School
Department
Course
Professor
Document Summary
Living organisms can be viewed and studied at different levels of organization. From atoms : the smallest component of an element. To the biosphere: all places on earth where living organisms exist. The smallest functional units of matter that form all chemical substances. Cannot be further broken down into other substance by ordinary chemical or physical means. Each specific type of atom is a chemical element: ex. Atomic nucleus: centre of the atom where protons and neutrons are confined. Entire atom has no net electric charge. In early 1900s, most scientists believed that the positive charge and mass of an atom were evenly dispersed throughout the atom: (cid:498)plum pudding(cid:499) atomic model, electrons are like plums dispersed in a positively charged pudding. Rutherford tested this model: hypothesized that atoms in a thin sheet of gold foil would be composed of diffuse, evenly distributed positive charges that would cause alpha particles to be slightly deflected as they pass through.
