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Compounds & Molecules NaCl, salt Buckyball, C 60
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Compounds & Molecules COMPOUNDS are a combination of 2 or more elements in definite ratios by mass.COMPOUNDS are a combination of 2 or more elements in definite ratios by mass. The character of each element is lost when forming a compound.The character of each element is lost when forming a compound. MOLECULES are the smallest unit of a compound that retains the characteristics of the compound.MOLECULES are the smallest unit of a compound that retains the characteristics of the compound.
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ELEMENTS THAT EXIST AS DIATOMIC MOLECULES
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ELEMENTS THAT EXIST AS MOLECULES Allotropes of C
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ELEMENTS THAT EXIST AS POLYATOMIC MOLECULES White P 4 and polymeric red phosphorus S 8 sulfur molecules
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Molecular Compounds Compounds without Ions CH 4 methane CO 2 Carbon dioxide BCl 3 boron trichloride
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MOLECULAR FORMULAS Formula for glycine is C 2 H 5 NO 2Formula for glycine is C 2 H 5 NO 2 In one molecule there areIn one molecule there are –2 C atoms –5 H atoms –1 N atom –2 O atoms
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STRUCTUAL FORMULAS Can also write glycine formula as –H 2 NCH 2 COOH to show atom ordering structural formulaor in the form of a structural formula
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MOLECULAR MODELING Ball & stick Space-filling Drawing of glycine
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Naming Elements & Compounds Chapter 2 & 3: Chemical Equations Handbook BCl 3 boron trichloride CO 2 Carbon dioxide molecules are formed from two or more nonmetals. Ionic compounds have a cation and anion: generally involve a metal and nonmetal, NaCl ammonium chloride, NHCl ammonium chloride, NH 4 Cl
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IONS AND IONIC COMPOUNDS IONS are atoms or groups of atoms with a positive or negative charge.IONS are atoms or groups of atoms with a positive or negative charge. Taking away an electron from an atom gives a CATION with a positive chargeTaking away an electron from an atom gives a CATION with a positive charge Adding an electron to an atom gives an ANION with a negative charge.Adding an electron to an atom gives an ANION with a negative charge.
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Forming Cations & Anions A CATION forms when an atom loses one or more electrons. An ANION forms when an atom gains one or more electrons Mg --> Mg 2+ + 2 e- F + e- --> F -
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CATION + ANION ---> COMPOUND COMPOUND CATION + ANION ---> COMPOUND COMPOUND Are NEUTRAL. Compounds have EQUAL number of + EQUAL number of + and - charges. Are NEUTRAL. Compounds have EQUAL number of + EQUAL number of + and - charges. COMPOUNDS FORMED FROM IONS Na + + Cl - --> NaCl
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IONIC COMPOUNDS NH 4 + Cl - ammonium chloride, NH 4 Cl
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Properties of Ionic Compounds Forming NaCl from Na and Cl 2 A metal atom can transfer an electron to a nonmetal.A metal atom can transfer an electron to a nonmetal. The resulting cation and anion are attracted to each other by electrostatic forces.The resulting cation and anion are attracted to each other by electrostatic forces.
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Electrostatic Forces The oppositely charged ions in ionic compounds are attracted to one another by ELECTROSTATIC FORCES. These forces are governed by COULOMB’S LAW.
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Electrostatic Forces COULOMB’S LAW Direct relationship between charge and force: charges increase, the force increases. Inverse relationship between distance between ions and force: increase distance, decrease force. increase distance, decrease force.
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Importance of Coulomb’s Law NaCl, Na + and Cl -, m.p. 804 o C MgO, Mg 2+ and O 2- m.p. 2800 o C
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PREDICTING ION CHARGES In general metals (Mg) lose electrons ---> cationsmetals (Mg) lose electrons ---> cations nonmetals (F) gain electrons ---> anionsnonmetals (F) gain electrons ---> anions
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METALS M ---> n e- + M n+ where n = periodic group Na + sodium ion Mg 2+ magnesium ion Al 3+ aluminum ion Transition metals --> M 2+ or M 3+ are common Fe 2+ iron(II) ion Fe 3+ iron(III) ion
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NONMETALSNONMETALS NONMETAL + n e- ------> X n- where n = 8 - Group no. C 4-,carbide N 3-, nitride O 2-, oxide S 2-, sulfide F -, fluoride Cl -, chloride Group 7AGroup 6A Group 4A Group 5A Br -, bromide I -, iodide
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Charges on Common Ions +3 -4-2-3 +1 +2 By losing or gaining e-, atom has same number of e-’s as nearest Group 8A atom.
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Predicting Charges on Monatomic Ions
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Binary Ionic Compounds Mn 2+ + O 2- ----> MnO manganese (II) oxide Al 3+ + S 2- ----> Al 2 S 3 aluminum sulfide Sn 4+ + Cl - ----> SnCl 4 Tin (IV) chloride or Stannic chloride calcium fluoride Ca 2+ + 2 F - ---> CaF 2
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Practice Name & Formulas Ultimate Equation Handbook Only the binary compounds Exercise 2-1 pg. 10 Exercise 3-2 pg 17 Homework: Worksheets pgs 23-28
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POLYATOMIC IONS Groups of atoms with a charge. MEMORIZE the names and formulas in Table 3.1, page 89.
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Polyatomic Ions NH 4 + ammonium ion One of the few common polyatomic cations
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Polyatomic Ions HNO 3 nitric acid NO 3 - nitrate ion
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Polyatomic Ions CO 3 2- carbonate ion HCO 3 - bicarbonate ion hydrogen carbonate
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PO 4 3- phosphate ion CH 3 CO 2 - acetate ion Polyatomic Ions
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SO 4 2- sulfate ion SO 3 2- sulfite ion Polyatomic Ions
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NO 3 - nitrate ion NO 2 - nitrite ion Polyatomic Ions
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“ates” Worksheet pg #22
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Practice Name & Formulas Ultimate Equation Handbook Add the polyatomic compounds Exercise 2-1 pg. 10 Exercise 3-2 pg 17 Exercise 4-1 pg 20 Exercise 4-3 pg 21 Homework: Worksheets pgs 23-28 –poly Pgs 29-33
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Molecular & Ionic Compounds Heme NaCl
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