CHEM 4 Lecture Notes - Lecture 1: Unified Atomic Mass Unit, Weighted Arithmetic Mean, Atomic Number

• School: UCSD
• Department: Chemistry and Biochemistry
• Course: CHEM 4
• Professor: Carl Hoeger

Document Summary

Z: atomic number or nuclear charge (# of protons) Element a substance that only contains atoms with the same nuclear charge. Older def of element substance that can"t be broken down into any simpler substances by physical or chemical means (while retaining its chemical identity) Compound a substance composed of two or more elements which are chemically bonded. >coulomb"s law bigger charges on cation and anion, closer they are, stronger bond. Molecule - structure of two or more elements that are chemically bound together and behave as an independent unit. N = number of neutrons in nucleus. Isotopes - atoms of element with the same number or protons, but a different number of neutrons. Carbon: c (a=12, z=6), c (a=a3, z=6), c(a=14,z=6) The only difference is that in some cases, isotopes can be radioactive; number of neutrons (too many, too few) in nucleus impacts stability of the element.