The Chemistry of Life Chapter 2 The Nature of Matter Section 2-1 Biology 102

Chemistry Study of chemistry begins with the atom Atom – basic unit of matter Means indivisible

Atom Contains subatomic particles Proton Neutron Electron Positive charge Neutron No charge Highest mass Electron Negative charge Constantly in motion and high energy motion keeps electrons outside nucleus

Atom Nucleus – Center of atom that contains protons and neutrons All atoms are neutral P = E Atomic # - number of protons Atomic mass – protons + neutrons

Elements and Isotopes Element – pure substance that consists entirely of one type of atom Over 100 known 12 common in living organisms Ex: C, H, N

Isotopes Isotope – atoms of the same element with differing number of neutrons Identified by their mass numbers (average) All isotopes have the same chemical numbers Ex: hydrogen, deuterium, tritium

Radioactive Isotopes Unstable nuclei and nuclei break down over time Radiation is dangerous, but can be advantageous

Chemical Compouds Compounds – two or more elements combined together Ex: H20, NaCl Physical and chemical properties of the compound differ from the original elements Ex: NaCl

Chemical Bonds Atoms do not have the same ability to attract electrons Due to this, usually one atom in a bond will pull the electrons closer to it than the other atom. Creates partial negative and positive charges Creates van der Waals forces Slight attraction that develops between oppositely charged regions of nearby molecules. Ex: Gecko