CHE 100 Lecture Notes - Lecture 7: Mass Number, Nucleolus

• School: University at Buffalo
• Department: Chemistry
• Course: CHE 100
• Professor: Clarke Priscilla

Document Summary

A chemical reaction involves the union or separation of individual atoms. J. j. thompson discovered that atoms are composed of even smaller particles: Electrons, protons, and neutrons are the three atomic particles. Fired alpha particles (radiation) at gold foil sheets. Observed that most of the alpha particles went straight through the foiling. Based on this observation, he concluded that atoms are mostly empty space occupied by the electrons spread throughout the atom. He also discovered the nucleus = a positively charged unit in the center of the atom that contains the protons and neutrons. Positively charged nucleus, which contains protons and neutrons, surrounded by electrons spread throughout the atom. Mass number = number of protons + number of neutrons for a specific atom (a) Law of conservation of matter = when a reaction takes place, matter is neither created or destroyed.