BIOL 2404 Chapter Notes - Chapter 2: Thymine, Glycogen, Particle Size
Document Summary
Composition of matter: elements: unique substances that cannot be broken down by ordinary chemical means, atoms: more-or-less identical building blocks for each element, atomic symbol: one- or two-letter chemical shorthand for each element. Identification of elements: atomic number: equal to the number of protons, mass number: equal to the mass of the protons and neutrons, atomic weight: average of the mass numbers of all isotopes. Isotope: atoms with same number of protons but a different number of neutrons. Ionic bonds form between atoms by the transfer of one or more electrons. Ions: charged atoms resulting from the gain or loss of electrons: anions: negatively charged ions due to gaining one or more electrons, cations: positively charged ions due to losing one or more electrons. Ionic compounds form crystals instead of individual molecules: example: nacl (sodium chloride) Polar and nonpolar molecules: electrons shared equally between atoms produce nonpolar molecules, unequal sharing of electrons produces polar molecules.
