The Chemistry of Life Why are we studying chemistry? Chemistry is the foundation of Biology Proton Neutron Electron Hydrogen 1 proton 1 electron Oxygen 8 protons 8 neutrons 8 electrons + 0 ? Everything is made of matter Matter is made of atoms The World of Elements C Different kinds of atoms = elements H O N P S Na K Mg Ca Life requires ~25 chemical elements About 25 elements are essential for life Four elements make up 96% of living matter: ? carbon (C) ? hydrogen (H) ? oxygen (O) ? nitrogen (N) Four elements make up most of remaining 4%: ? phosphorus (P) ? calcium (Ca) ? sulfur (S) ? potassium (K) Effect of electrons electrons determine chemical behavior of atom depends on number of electrons in atom?s outermost shell valence shell Bonding properties