Chem+Basics

__**Chem Basics:**__
atoms:basic unit of matter
 * the subatomic particles that make up atoms are protons, neutrons, and electrons
 * atos are extremely small
 * protons and neutrons have the same mass
 * protons are positively charged, neutrons have no charge, and electrons are negatively charged
 * protons and neutrons are bond together to form the nucleus
 * electrons are in constant motion in the space surrounding the nucleus

elements and isotopes:
 * an element is a pure substance that consists entirely of one type of element
 * an isotope is an atom of an element that has anumber of neutrons different from that of other atoms of the same element
 * all isotopes have the same chemical properties, beacause they have the same number of electrons

chemical bonds: the main types of chemical bonds are ionic and covalent bonds
 * ionic bond is formed when one or more electrons are transferred from one atom to another[[image:http://kimia.cikgupaatz.com/wp-content/uploads/2010/08/covalent_bonding.gif width="216" height="150" align="right"]]
 * covalent bond forms when electrons are shared between atoms
 * the electrons available to form bonds are called valence electrons
 * atoms that lose electrons have a positive charge
 * atoms that gain electrons have a negative charge
 * when the atoms share two electrons, the bond is called a single covalent bond

van der Waals forces: a slight attraction that develops between the oppositely charged regions of nearby molecules
 * are not as strong as covalent and ionic bonds
 * can hold molecules together
 * ex) van der Waals forces help geckos grip smooth, vertical surfaces

water molecule:
 * a water molecule is neutral
 * polar molecule: molecule in which the charges are unevenly distributed
 * a water molecule is polar because there is an uneven distribution of electrons between the oxygen and hydrogen atoms

hydrogen bonds: acids, Bases, and pH: videos:
 * not as strong as covalent or ionic bonds
 * ex) the attraction between the hydrogen atom on one water molecule and the oxygen atom on another water molecule
 * water is etremely cohesive, due to hydrogen bonding
 * ph scale:
 * scale ranges from 0 to 14
 * solutions with a pH below 7 are acidic, solutions with a ph above 7 are basic, and solutions with the pH of seven are neutral( pure water has a pH of seven)
 * acidic solutions contain higher concentrations of H+ ions than pure water and have pH values lower than 7
 * [[image:http://www.rcsd.ms/~rawest/ph%20Scale.gif width="244" height="312" align="right"]]ex) stomach acid, lemon juice, tomato juice, acid rain, and normal rainfall
 * basic, or alkaline, solutions contain lower concentrations of H+ ions than pure water and have a pH above 7
 * ex) oven cleaner, bleach, ammonia solution. soap, sea water, and human blood
 * Making Molecules with Atoms
 * Ionic and covalent bonding animation
 * Bill Nye the science guy: Atoms and Molecules