I. Why Atoms Combine Chemical Formula Chemical Bond Stability

What is a compound? What does the word compound mean in this sentence? “I have a compound fracture in my leg.”

What is a compound? Compounds involve more than one element/atom. Table salt is a compound made of two elements, sodium (Na) and chlorine (Cl).

What is a compound? A compound always has the same chemical formula. Remember that a chemical formula helped you to categorize a substance as a mixture or a compound a few chapters ago.

H2O A. Chemical Formula Shows: 1) elements in the compound 2) ratio of their atoms H2O 1 oxygen atom 2 hydrogen atoms

Practice Silver chloride = one atom of silver + one atom of chlorine _______________________ Hydrochloric acid = one atom of hydrogen + one atom of chlorine ________________________

Potassium chloride = one potassium atom + one chlorine atom ammonium bromide = one atom of nitrogen + four atoms of hydrogen + one atom of bromine

Practice Hydrogen peroxide= two atoms of hydrogen + two atoms of oxygen ______________________ Magnesium carbonate = one atom of magnesium + one atom of carbon + three atoms of oxygen __________________________

Practice Glucose = six atoms of carbon + twelve atoms of hydrogen + six atoms of oxygen _______________________ sucrose, C12H22O11 Show me the elements and atom amount

B. Chemical Bond Strong attractive force between atoms or ions in a molecule or compound. The higher the melting and boiling points of a substance, the stronger the attractive forces.

C. What is an ion? An ion is an atom with a net charge because it no longer has the same number of electrons and protons. An ion is formed when atoms need to give up or take electrons to fill their outer energy level.

Ions Going back to sodium (Na) and chlorine (Cl) forming table salt, sodium gave up an electron to chlorine. So sodium chloride is made of sodium and chlorine ions. Both elements now have a charge.

Chemical bonds Formed by either: transferring e- (losing or gaining) sharing e-

Ne D. Stability Octet Rule most atoms form bonds in order to have 8 valence e- full outer energy level like the Noble Gases! Ne Stability is the driving force behind bond formation!

C. Stability Transferring e- Sharing e-

II. Kinds of Chemical Bonds Ionic Bond Covalent Bond Comparison Chart

A. Ionic Bond Attraction between 2 oppositely charged ions Ions - charged atoms formed by transferring e- from a metal to a nonmetal

A. Ionic Bond ions form a 3-D crystal lattice NaCl

A. Oxidation Number The charge on an ion. Indicates the # of e- gained/lost to become stable. 1+ 2+ 3+ 4+ 3- 2- 1-

Metallic Bonds Metals: can conduct electricity flexible can be hammered into thin sheets stretched into thin wire

Metallic Bonds Electrons move freely between metal atoms Metal atoms pack closely together so their outer orbitals (energy levels) overlap So electrons are free to move from atom to atom

Metallic Bonds Valence electrons of metals are not associated with a particular metal ion. This helps electricity to move fast along metal wires.

B. Covalent Bond Attraction between neutral atoms formed by sharing e- between two nonmetals

B. Covalent Bond covalent bonds result in discrete molecules NH3 H2O Cl2

Covalent Bond –sharing

B. Covalent Bond Nonpolar Covalent Bond e- are shared equally usually identical atoms

+ - B. Covalent Bond Polar Covalent Bond e- are shared unequally between 2 different atoms results in partial opposite charges + -

B. Covalent Bond Nonpolar Polar Ionic View Bonding Animations.

C. Comparison Chart IONIC COVALENT transferred from metal to nonmetal shared between nonmetals Electrons Melting Point high low Soluble in Water yes usually not yes (solution or liquid) Conduct Electricity no crystal lattice of ions, crystalline solids molecules, odorous liquids & gases Other Properties

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III. Naming Molecular Compounds Molecular Names Molecular Formulas Chemical Bonds III. Naming Molecular Compounds Molecular Names Molecular Formulas

A. Molecular Names Write the names of both elements. Change the final ending to -ide. Add prefixes to indicate subscripts. Only use mono- prefix with oxide.

A. Molecular Names PREFIX mono- di- tri- tetra- penta- SUBSCRIPT 1 2 3 4 5

A. Molecular Names PREFIX hexa- hepta- octa- nona- deca- SUBSCRIPT 6 7 8 9 10

A. Molecular Names CCl4 N2O carbon tetrachloride SF6 dinitrogen monoxide sulfur hexafluoride

B. Molecular Formulas Write the more metallic element first. Add subscripts according to prefixes.

B. Molecular Formulas phosphorus trichloride dinitrogen pentoxide PCl3 dihydrogen monoxide PCl3 N2O5 H2O

B. Molecular Formulas The Seven Diatomic Elements Br2 I2 N2 Cl2 H2 O2 F2

IV. Naming Ionic Compounds Oxidation Number Ionic Names Ionic Formulas Chemical Bonds IV. Naming Ionic Compounds Oxidation Number Ionic Names Ionic Formulas

A. Oxidation Number The charge on an ion. Indicates the # of e- gained/lost to become stable. 1+ 2+ 3+ 4+ 3- 2- 1-

B. Ionic Names Write the names of both elements, cation first. (metal) Change the anion’s ending to -ide. (nonmetal) For ions with variable oxidation #’s, write the ox. # in parentheses using Roman numerals. Overall charge = 0. (Transition metals)

B. Ionic Names NaBr Be3P2 sodium bromide Beryllium phosphide

C. Ionic Formulas Write each ion. Put the cation first. Overall charge must equal zero. If charges cancel, just write the symbols. If not, crisscross the charges to find subscripts.

C. Ionic Formulas potassium chloride K+ Cl-  KCl

C. Ionic Formulas Na+ + O2- ---> Na2O calcium oxide Ca2+ O2-  CaO Sodium oxide Na+ + O2- ---> Na2O

Ionic Formulas Aluminum chloride Al3+ + Cl- ---> AlCl3

Covalent Bond Naming SiO2 silicon dioxide NO nitrogen monoxide XeF4 Xenon tetrafluoride

Covalent Bond Naming Tetraphosphorus trisulfide P4S3 PBr3 phosphorus tribromide CS2 carbon disulfide

Covalent bond formula Nitrogen trifluoride NF3 Dinitrogen pentoxide N2O5

Covalent Bond formula Trisilicon tetranitride Si3N4 Carbon dioxide CO2