CHEM 111 Lecture Notes - Lecture 4: Atomic Number, Mass Number, Relative Atomic Mass

• School: UMASS-Amherst
• Department: Chemistry
• Course: CHEM 111
• Professor: Julian Tyson

Document Summary

Chem111 lecture 4 atoms and the periodic table. Electrons do not occupy all the same space, there is a structure. If an atom is neutral, then the number of protons are the same as the number of electrons. Mass number goes on the top left hand corner. Atomic number goes on the bottom left hand corner. There are no units when describing the relative mass of an atom. The masses that we see on the periodic table are atomic weight. The mass of an atom is the number of neutrons plus the number of protons. We can get stable atoms of carbon with different numbers on neutrons. Isotopes atoms with the same number of protons and electrons but with a different number of neutrons.