Nature

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

Chapter 2 The Chemical Context of Life Basic Terms Element = cannot be broken down to other substances Examples: Na, O, C, Cl Compound = combination of 2 or more different elements Examples: NaCl, CO2, CH4 Requirements for Life 92 natural elements? 25 are essential to life Carbon, oxygen, hydrogen, and nitrogen make up 96% of living matter Trace elements are needed, too, though Iodine?lack of = goiter!! Atomic Structure Atom = smallest possible amount of an electron that retains the element?s properties Subatomic particles: Protons = + charge Electrons = - charge Neutrons = neutral charge Atomic Structure Atomic Number: # of protons (also equals # of electrons?) Mass Number: # of protons + # of neutrons Examples Isotopes