CHEM 1151 Lecture Notes - Lecture 1: Unified Atomic Mass Unit, International System Of Units, Mass Spectrometry

• School: Northeastern University
• Department: Chemistry & Chemical Biology
• Course: CHEM 1151
• Professor: Patricia A.Mabrouk

Document Summary

1/2 mass of 12c essentially mass of a proton/neutron neutrons: electrically neutral, mass = 1. 009amu protons: positively charged (1. 602x10-19c), mass 1. 007amu. Outside nucleus electron: negatively charged (-1. 602x10-19c), mass = 5. 5x10-4 amu. Coulomb interaction electrostatic attraction (coulombic force) between protons and electrons. Elements atoms with different numbers of protons have different physical and chemical properties normally electrically neutral (same number of protons and neutrons) Cations, xn+ some elements lose electrons readily protons > electrons charge, n, is positive and equal to difference between number of protons and electrons. Anions, xn- gain electrons readily electrons > protons n is negative and difference between number of protons and electrons. Z: # of protons characterize atoms of an element. Isotopes atoms of an element that differ in # of neutrons they have. A: total # of protons and neutrons weighted average of the atomic masses of an element"s naturally occurring isotopes. Mass spectrometer components: ionization source, analyzer, detector electron impact ionization electron impact ionization.