8: Atomic Mass, Reaction Stoichiometry
-
- 8.1: Isotopes and Atomic Weights
- Isotopes are atoms of the same element that contain different numbers of neutrons. For these species, the number of electrons and protons remain constant. This difference in neutron amount affects the atomic mass (A) but not the atomic number (Z). In a chemical laboratory, isotopes of an element appear and react the same.
-
- 8.2: The Mole
- When objects are small or come in larger quantities, it is often inconvenient, inefficient, or even impossible to deal with the objects one at a time. For these reasons, we often deal with small objects or large quantities in groups, and have even invented names for various numbers of objects.
-
- 8.6: Grams-->Moles-->Moles-->Grams
- As we just discussed, molar mass is defined as the mass (in grams) of 1 mole of substance (or Avogadro's number of molecules or formula units). The simplest type of manipulation using molar mass as a conversion factor is a mole-gram conversion (or its reverse, a gram-mole conversion).
Thumbnail: Visual of how the law of conservation of mass means that there must be same number of atoms of each element for the reactants and the products. (CC BY-SA 4.0; Enoshd via Wikimedia )