CHEM 110 Chapter Notes - Chapter 1: Unified Atomic Mass Unit, Relative Atomic Mass, Molecular Mass
Document Summary
Vast majority of the volume is empty space. Electron: negatively charged; occupies empty space of the volume. Neutron + proton = virtually all of the mass of the atom. Because # of electrons = # of protons. Chemical identity of an atom designated by an atomic number. Atomic number: determined by the number of protons in the nucleus. Atoms can differ by the number of neutrons in their nuclei (and mass) Isotopes: atoms of the same element with different numbers of neutrons. Can occur naturally or be synthetically produced in nuclear reactions. Atomic weight is the average of the masses of all isotopes present. Atomic weight = [(isotope mass) x (fractional natural abundance)] *ex: naturally occurring carbon is 98. 93% carbon 12 (12 amu mass) and. Atomic weight = (0. 98930)(12 amu) + (0. 0107)(13. 00335 amu) Atomic mass unit (amu): exactly 1/12 of the mass of one atom of the carbon-12 isotope.
