CEM 151 Chapter Notes - Chapter 2: Ope, Nonmetal, Robert Andrews Millikan
Document Summary
The total mass of materials present after a chemical reaction is the same as the total mass present before the reaction. In a given compound, the relative numbers and the kinds of atoms are constant. All samples of a given compound, regardless of their source or how they were prepared, have the same proportions of their constituent elements. If two elements, a and b combine to form more than one compound, then the mass of b, which combines the mass of a, is a ratio of small whole numbers. Protons: found in the nucleus have a positive charge equal in magnitude to the electron"s negative charge. Electrons:found outside the nucleus, take up most of the volume of the atom, have a negative charge. Neutrons: found in the nucleus, virtually same mass as proton but no charge. Mass: 1. 67 x 10 - 27 kg = 1 amu. When atoms or molecules gain or lose electrons, they become ions.
