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  loses valence electrons. Form positive ions (cations ) Have most of their valence electrons. High ionization energy  gains 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.

Covalent Bonds Chemical bond when two atoms share valence electrons. Sharing counts towards full valence. Occurs between two nonmetals.

Covalent Bond Diagrams Molecular formulaOrbital diagram Structural formula

Diatomic Elements Prefix “di” = 2 Nonmetallic atoms that form covalent bonds with same type of atom.

Polar Covalent Bonds Covalent bond where electrons spend more time around one atom than the other. One side of molecule positive, other is negative. Water molecules (H 2 O) have polar covalent bonds.

Metallic Bonds Metals have low ionization energy. Valence electrons float freely between metal cations. No compounds with two metals.

Carbon Chemistry Carbon makes many compounds because it can make 4 covalent bonds. Organic Compounds contain both Carbon (C) and Hydrogen (H). Hydrocarbons are organic compounds ONLY made of Hydrogen and Carbon.

GraphiteDiamond GraphiteDiamond

Isomers A molecule that has the same chemical formula as another molecule (meaning the same #of atoms) is known as an isomer.

Saturated hydrocarbon, all carbon atoms form single covalent bonds with hydrogen. (Ex: C 2 H 6 ) Unsaturated hydrocarbons make at least one double or triple covalent bond in the molecule (Ex: C 2 H 4 ) Saturated and Unsaturated Hydrocarbons.