BIOL 102 Chapter Notes - Chapter 2: Atomic Mass, Chemical Element, Unified Atomic Mass Unit
Document Summary
Atom: smallest functional unit of matter (cannot be broken down), each occur as a chemical element. Nucleus: consists of protons and neutrons confined to a very small volume. The amount of neutrons and protons cannot vary in an atom; however, the amount of electrons can vary. Rutherford"s hypothesis: alpha particles should slightly be deflected when passing through a plate of gold foil. Therefore, most of the atom is empty space, with positive charges concentrated in small volumes. Only if the alpha particles hit directly the nucleus would the be deflected. An orbital can contain max of 2 electrons. The electrons with the lowest amount of energy fill orbitals first. Valence (outer) electrons: allow atoms to form chemical bonds with one another. Atomic mass is measures in daltons (da) (a. k. a john dalton) Weight refers to the gravitational pull on a mass. (mass is the same in all locations) Mole (term) developed to know the number of atoms rather than mass.
