Chemical Formulas Shows which atoms are found in each substance Subscripts – how many of each atom. NaCl = one sodium and one chlorine. CaCl 2 = one calcium and two chlorines. Coefficients – how many of each unit (multiplier). 2H 2 O = 2 H 2 O molecules (4 total hydrogen, 2 total oxygen)

Chemical Bonds Chemical bonds form when two atoms share or exchange valence electrons. Octet rule – atoms attempt to have a full valence.

Ions: Matter with a charge An Ion is an atom or molecule where the number of electrons does not equal the number of protons (will have positive or negative charge). Ions are written with a charge in superscript. Examples of Ions: H+H+ Cl - Mg 2+

High Ionization Energy Elements gain valence electrons (nonmetals)

Valence Electrons and Ionization Energy MetalsNonmetals Have few valence electrons. Low ionization energy  lose valence electrons. Form positive ions (cations ) Have most of their valence electrons. High ionization energy  gain valence electrons. Form negative ions (anions)

Ionic Bonds Chemical bond that form from ions with opposite charges. One atom loses valence electrons to another (usually metal loses to nonmetal) Salt formation - ions

Ionic Compounds Brittle crystalline solids with high melting points. Ionic bonds make compound overall neutral. Crystals – solids with orderly arrangement of atoms. Good insulators as solids, good conductors when melted or dissolved in water.

Lewis Dot Structures and Ions Can determine type of ion and charge from periodic table. Metals make cations (+), nonmetals make anions (-).

Ion Charges from Periodic Table Pattern more complicated for transition metals.

What is an acid? A compound when dissolved in water creates hydrogen ions (H + ) The H + ion bonds with water molecules and form hydronium ions (H 3 O + )

Ionization of an Acid

Properties of Acids Sour taste Corrosive (reacts with metals). Strong acids can burn organic tissue. Reacts with an indicator (ex. Litmus paper) to turn it a red color.

Bases A chemical that creates hydroxide ions (OH - ) when dissolved in water. Bases produce hydrogen ions (H + ) in solution like acids, but have more hydroxide ions (OH - ) than hydrogen ions (H + ).

Properties of Bases Bitter Taste Slippery feel when dissolved in water. Are corrosive Strong bases can burn organic tissue.

pH – (Think power of H + ) pH measures the amount of hydrogen ions (H + ) in a solution. pH of acids (0 – 6.9) pH of bases (7.1 – 14) pH of 7 is neutral (neither acid or base). Pure water has a pH of 7.