Biology Basic Chemistry

Matter and Atomic Structure Atom: the smallest particle of an element; consists of: Protons p+: in the nucleus Neutrons no: in the nucleus Electrons e-: surrounds the nucleus; equal to the number of protons

Matter and Atomic Structure Matter: anything that has volume and mass Element: a substance not broken down into simpler substances by physical or chemical means Each element has a 1 or 2-letter symbol Examples: oxygen (O), sodium (Na) Molecule:A molecule is formed when two or more atoms join together chemically. Ex: hydrogen (H2), oxygen (O2) and nitrogen (N2) Compound: a molecule composed of atoms of 2+ different elements that are chemically combined Ex: NaCl: salt, H2O: water

Matter and Atomic Structure Atomic Number: the number of protons in an atom’s nucleus Mass Number: the number of protons and neutrons in an atom Energy levels: the area of an atom surrounding the nucleus where electrons are found # of protons always equals the # of electrons; atoms have NO CHARGE

Energy Levels First energy level: holds up to 2 electrons Second energy level: holds up to 8 electrons

Copyright Pearson Prentice Hall Chemical Bonds The main types of chemical bonds are: ionic bonds covalent bonds Copyright Pearson Prentice Hall 6

Copyright Pearson Prentice Hall Chemical Bonds Ionic Bonds An ionic bond is formed when one or more electrons are transferred from one atom to another. These positively and negatively charged atoms are known as ions. Copyright Pearson Prentice Hall 7

Copyright Pearson Prentice Hall Chemical Bonds Sodium atom (Na) Sodium ion (Cl-) The chemical bond in which electrons are transferred from one atom to another is called an ionic bond. The compound sodium chloride forms when sodium loses its valence electron to chlorine. Copyright Pearson Prentice Hall 8

Copyright Pearson Prentice Hall Chemical Bonds Covalent Bonds Sometimes electrons are shared by atoms instead of being transferred. Copyright Pearson Prentice Hall 9

Copyright Pearson Prentice Hall Chemical Bonds A covalent bond forms when electrons are shared between atoms. Copyright Pearson Prentice Hall 10

Copyright Pearson Prentice Hall Chemical Bonds The structure that results when atoms are joined together by covalent bonds is called a molecule. Copyright Pearson Prentice Hall 11

Copyright Cmassengale Water About 60-90 percent of an organism is water Water is used in most reactions in the body Water is called the universal solvent Copyright Cmassengale 12 12

Copyright Pearson Prentice Hall The Water Molecule Water Molecule The unequal sharing of electrons causes the water molecule to be polar. The hydrogen end of the molecule is slightly positive and the oxygen end is slightly negative. Copyright Pearson Prentice Hall 13

Copyright Cmassengale Water Properties Polarity Cohesiveness Adhesiveness Surface Tension Copyright Cmassengale 14 14

Copyright Pearson Prentice Hall The Water Molecule A water molecule is polar because there is an uneven distribution of electrons between the oxygen and hydrogen atoms. Copyright Pearson Prentice Hall 15

Copyright Pearson Prentice Hall The Water Molecule Hydrogen Bonds Because of their partial positive and negative charges, polar molecules can attract each other. Copyright Pearson Prentice Hall 16

Copyright Pearson Prentice Hall The Water Molecule Cohesion is an attraction between molecules of the same substance. Because of hydrogen bonding, water is extremely cohesive. Example: surface tension (bugs walking on water) Copyright Pearson Prentice Hall 17

Copyright Pearson Prentice Hall The Water Molecule Adhesion is an attraction between molecules of different substances. Copyright Pearson Prentice Hall 18

Solutions and Suspensions A mixture is a material composed of two or more elements or compounds that are physically mixed but not chemically combined. Copyright Pearson Prentice Hall 19

Solutions and Suspensions Two types of mixtures can be made with water solutions suspensions Copyright Pearson Prentice Hall 20

Solutions and Suspensions All the components of a solution are evenly distributed throughout the solution. solute—the substance that is dissolved. solvent—the substance in which the solute dissolves. Copyright Pearson Prentice Hall 21

Solutions and Suspensions When a crystal of table salt is placed in warm water, sodium and chloride ions are attracted to the polar water molecules. Na+ Cl - Water When an ionic compound such as sodium chloride is placed in water, water molecules surround and separate the positive and negative ions. Copyright Pearson Prentice Hall 22

Solutions and Suspensions Some materials do not dissolve when placed in water but separate into pieces so small that they do not settle out easily. Copyright Pearson Prentice Hall 23

Acids & Bases Acid: any compound that forms H+ ions in solution Base: any compound that forms OH- in solution Water can dissociate to form acids and bases H20 H+ + OH-

pH Scale A measurement system indicating concentration of H+ or OH- ions in a solution Ranges from 0-14 0-6.99 = acidic solution 0 more acidic than 6.99 7.1-14 = basic solution (alkaline) 14 more basic than 7.1

**This scale can be presented 0-14 OR 14-0** http://pearl.maine.edu/windows/community/Water_Ed/pH/pH_whatisit_clip_image001.gif **This scale can be presented 0-14 OR 14-0**