Biology Basic Chemistry – Chapter 2 Section 1 and 2

Matter and Atomic Structure  Atom: the smallest particle of an element; consists of: Protons p + : in the nucleus Neutrons n o : 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, may or may not be the same atom. Ex: hydrogen (H 2 ) and water (H 2 0) atomshydrogen Compound: a molecule composed of atoms of 2+ different elements that are chemically combined Ex: NaCl: salt, H 2 O: 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: Two types (Ionic & Covalent) 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 Chemical Bonds A covalent bond forms when electrons are shared between atoms.

8 Water – A Molecule  About percent of an organism is water Water is used in most reactions in the body Water is called the universal solvent Copyright Cmassengale

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 The Water Molecule Hydrogen Bonds (Weak Bonds) Because of their partial positive and negative charges, polar molecules can attract each other. – Polar Covalent

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 The Water Molecule Adhesion is an attraction between molecules of different substances. Capillary Action

Copyright Pearson Prentice Hall Suspensions and Solutions A mixture is a material composed of two or more elements or compounds that are physically mixed but not chemically combined. Two types of mixtures can be made with water Suspensions Solutions

Copyright Pearson Prentice Hall Suspensions and Solutions 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 Suspensions and Solutions Solutions 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 Suspensions and Solutions 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

Acids & Bases (Form in Solution)  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  H 2 0 H + + OH -

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

**This scale can be presented 0-14 OR 14-0**