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Formula Writing oxidation number-number assigned to keep track of electron gain or loss lose electron cation METALS - + gain electron anion (nonmetals) cation is written first anion is second positive ion first negative ion second Polyatomic Compounds Binary Compound Compound made of 3 or more elements Compound made of only two elements (Usually metal with nonmetal) Use Criss-Cross (Usually table E, polyatomic ions) Definition Use Criss-Cross Binary Compound Second element name ends in “-ide” Definition Aluminum Sulfide 1. Look up symbol for the element on Table S Al S 2. Write the oxidation number, (which are found on the Periodic Table, above each symbols as a superscript): Al +3 S-2 3. Crisscross the oxidation numbers and omit the charge signs. Write the numbers below the symbols as subscripts. Al2S3 Note: The crisscrossing of the oxidation numbers conserves the charge. The sum of the oxidation numbers of all of the atoms in a compound is always zero. 4. When each element has the same oxidation number, these numbers are dropped and the formula is correct as written in step 1. Polyatomic Compounds Second element can end in -”ate” -”ite” -”ium” ONLY -”ide’s”: “peroxide, hydroxide, cyanide Aluminum Sulfate 1. Look up symbol for the element on Table S; polyatomic ion on Table E Al SO4 2. Write the oxidation numbers, which are found on the Periodic Table, above each symbols as a superscript: Al +3 SO4-2 3.Place the polyatomic ion in parentheses Crisscross the oxidation numbers and omit the charge signs. Write the numbers below the symbols as subscripts. Al2(SO4)3 The sum of the oxidation numbers of all of the atoms in a compound is always zero. 4. When each element has the same oxidation number, these numbers are dropped and the formula is correct as written in step 1. Sodium Sulfide Na -ide on PT -ate on Table E S 2- +1 Na Sodium Sulfate +1 Na2S S 2- Na +1 SO4 2- ***MUST use parentheses hereif it’s more than one!*** Na2 SO4 Naming Compounds Ionic compounds Naming Binary Compounds 1. The element with the positive ionic charge is written first. 2. The second word is formed by changing the ending of the name of the element to “ide”. Example bromine becomes bromide. Metals usually have positive ionic charges Nonmetals (when combined with metals) have negative charges. NaCl Polyatomic Ions Look up the name of the polyatomic ion on chart table E When polyatomic ion is second 1. write the name of the first element 2. write the name of the polyatomic ion Na2SO4 Sodium sulfate If polyatomic ion first 1. look up ion name 2. follow ending for binary compounds NH4Cl sodium chlorine ammonium chlorine sodium chloride ammonium chloride Naming & Writing Compounds Elements with more than one positive oxidation number (Transition Metals) (This is called the Stock System) When the oxidation number varies we us a Roman numeral in parentheses to indicate the charge. Roman number is used for the positive element only!!! (I, II, III, IV, V, VI, VII, VIII, IX, X) FeO Iron (II) oxide Fe2O3 Iron(III) oxide Alternative method for compounds **TRANSITION METALS!!!!! ALL NON METALS ONLY!!! We can also use prefix to indicate the number of each element mon 1, di 2, tri 3, tetra 4, penta 5, hexa 6, hepta 7, octa 8, non 9, deca 10 ***No criss cross*** If the first element is 1, don’t write mono ALWAYS prefix for 2nd Carbon monoxide CO dinitrogen trioxide N2O3 Chemical Bonding Chemical bonds are the forces that hold atoms together in a compound. • when atoms bond they release energy and become more stable Ionic Covalent Metallic Ionic Bonds Metal/nonmetal e- is transferred from the metal to the nonmetal EN difference greater than 1.7 Greater the EN difference, greater the ionic character Transfer e- QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Ionic Solid hard crystalline high melting and boiling points do not conduct electricity in the solid state do conduct electricity in the molten (liquid) or aqueous state (aq)-electrolyte (ions) NaCl Covalent Bond Share e 2 nonmetals Nonpolar Polar Same nonmetals Different nonmetals Share the electrons equally Share the electrons unequally Difference of 0 Difference of 0.1-1.7 Cl2 H20 CO2 - Coordinate Moochers one atom donates a pair of electrons to be share, the other contributes none NH4+ H3O+ Qui ckTime™ and a TIFF (U ncompr essed) decompressor are needed to see thi s pi cture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Molecular Substance are brittle in the solid form All 3 states of matter are poor conducts of heat and electricity Low melting and boiling points C6H12O6 Network Solid Hard crystalline Are poor conductors of heat and electricity High melting boiling points C-diamond SiO2-quartz/sand SiC CO2 HCl QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Metallic Bonds Mobile e - metal Metals Electrons move freely from one atom to another. “sea of mobile electrons” + + + + + ++ + + + + + + - - - - - - - -- - - - - - - - - - ++++++++++++ good conductors of electricity and heat in any state malleable ductile high melting and high boiling points Venn diagram Ionic Covalent Venn diagram Ionic Forms when one atom donates electrons to another Exist between ions Holds ions together in an ordered 3-d array, called an ionic crystal Typically exist between atoms on opposite sides of the periodic table Results from electrostatic attraction between opposite charges Covalent Are forces acting between atoms to hold them together Forms when atoms share 2,4,6 electrons Builds molecules Can form when atoms make contact Either absorb or release energy when formed Create new species with chemical and physical properties unlike constituent atoms Form because atoms want to have complete outer shells Can be polar or non-polar Exist between neutral atoms Forms when atoms that tend to gain electrons come into contact with one another Generally form between atoms in the upper right hand corner of the periodic table Lewis Dot Structure Octet Rule molecules and ions need to have eight electrons in their valance level as the result of bond formation Hydrogen and helium want 2 Rules for drawing an atom. Shows the number of valence electrons for an individual atom Find the number of valence e Put 2 on top Put 1 on each side double up Ionic Metal/nonmetal OR an ION (just choose half)! Write the formula-tell how many of each atom you need Metal: Nonmetal: no dots 8 dots Aluminum bromide positive charge [ ] negative charge [ ] Covalent ***MOLECULE!!!!!!!*** ALL non metals 1. Look at the formula- find the element that’s only 1. (ex. H2O- the O) 2. Draw it like the atom (Limo Bus)- look up valence e-’s on PT. 3. Make sure electrons are in PAIRS!!!! 4. Complete the octet rule for all non-central atoms. 5. Check work. ** If it’s CARBON (C) …spread out the 4 electrons… ***Memorize the double and triple bonds. (O2, N2, CO2) Shapes and Polarity of Molecules (ALL NON-METALS!!!!) Determining Polarity Symmetrical non polar - opposite sides match Cross test Asymmetrical - polar opposite sides don’t match + ** MUST be symmetrical in both directions to be considered NonPolar. “SNAP” linear Check symmetry Definition 2 atoms connected 3 atoms in a line 1 central atom with 4 atoms around it Check symmetry No unpaired e around central atom tetrahedral pyramidal Always polar bent Always polar 1 central atom with 3 atoms around the central Atom 1 pair of e not shared 1 central atom, with 2 other atoms off the central atom 2 pairs of e not shared Ball and Stick Model Example HBr H Br CO2 O C O CH4 (non polar)H CH3F (polar) NH3 C H N H H2O H H H O H H H Shape Intermolecular Forces Are the forces that exist between individual molecules--weaker than a bond Hydrogen Bonding between molecules containing Hydrogen bonded with F, O, N small highly electronegative Dipole - Dipole dipole - polar molecule H-Br Atom with the higher EN will be negative. between polar molecules H-F **H-F H-Br *****H-Br Van der Waals London Dispersion between non polar molecules Diatomic elements Noble gases Organic-C Force is stronger: 1. Closer they are 2. Heavier they are CH4 ****CH4 Stronger the intermolecular force, higher the melting and boiling point Ionic > H-bond > Molecular (Covalent molecules) Molecule- Ion Attraction Ionic solids when placed in water dissociate ( separate) due to the attraction of opposite charges Polar and ionic (aq) NaCl (aq) Na+ Cl -