BIOL130 Lecture 1: Unit 2a Cellular Chemistry .docx
27 Feb 2015
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Document Summary
Four types of atoms make up 99% of matter found (c, h, o, n) Combined in complex macromolecules & simple forms (co2 (g) & h2o(l)) Nucleus: dense core made up of protons and neutrons. # of protons, defining characteristic = atomic number. Atomic mass = # of protons & # of neutrons. Electrons: negatively charged, orbit the nucleus, neglible mass. 2n^2 formula to find # of electrons per orbital. Atoms want their valence full to be stable, unpaired electrons participate in bonds. 1st shell = 2 electrons, 2nd shell = 8 electrons, 3rd shell = 8 electrons. Mass of 1 proton or neutron = amu/dalton (da) Hydrogen in the symbol h+ also is seen to present a proton. Column = group/family, same number of valence electrons, therefore same reactivity properties. Row = period, same number of orbitals. Elements abundance in organisms have at least one unpaired valence electrons and therefore are reactive with other elements and abundant in nature.
