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Presentation on theme: "Molecules and Ions Image courtesy of www.lab-initio.com."— Presentation transcript:

1 Molecules and Ions Image courtesy of

2 Molecules Two or more atoms of the same or different elements, covalently bonded together. Molecules are discrete structures, and their formulas represent each atom present in the molecule. Pentane, C 5 H 12

3 Covalent Network Substances Covalent network substances have covalently bonded atoms, but do not have discrete formulas. Why Not?? Graphene – carbon allotrope

4 IonsIons  Cation: A positive ion  Mg 2+, NH 4 +  Anion: A negative ion  Cl −, SO 4 2 −  Ionic Bonding: Force of attraction between oppositely charged ions.  Ionic compounds form crystals, so their formulas are written empirically (lowest whole number ratio of ions).

5 Predicting Ionic Charges Group 1: Group 1: Lose 1 electron to form 1+ ions H+H+H+H+ Li + Na + K+K+K+K+ Rb + Cs +

6 Predicting Ionic Charges Group 2: Loses 2 electrons to form 2+ ions Be 2+ Mg 2+ Ca 2+ Sr 2+ Ba 2+

7 Predicting Ionic Charges : Group 13 : Loses 3 electrons to form 3+ ions B 3+ Al 3+ Ga 3+

8 Predicting Ionic Charges Group 14: Loses 4 electrons or gains 4 electrons Caution! C 2 2- and C 4- are both called carbide

9 Predicting Ionic Charges Group 15: Gains 3 electrons to form 3- ions N 3- P 3- As 3- Nitride Phosphide Arsenide

10 Predicting Ionic Charges Group 16: Gains 2 electrons to form 2- ions O 2- S 2- Se 2- Oxide Sulfide Selenide

11 Predicting Ionic Charges Group 17: Gains 1 electron to form 1- ions F 1- Cl 1- Br 1- Fluoride Chloride Bromide I 1- Iodide

12 Predicting Ionic Charges Group 18: Stable Noble gases do not form ions!

13 Predicting Ionic Charges Groups : Groups : Many transition metals have more than one possible oxidation state. Iron(II) = Fe 2+ Iron(III) = Fe 3+

14 Predicting Ionic Charges Groups : Groups : Some transition metals have only one possible oxidation state. Zinc = Zn 2+ Silver = Ag +

15 Writing Ionic Compound Formulas Example: Barium nitrate 1. Write the formulas for the cation and anion, including CHARGES! Ba 2+ NO Check to see if charges are balanced. 3. Balance charges, if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Not balanced ( ) 2

16 Writing Ionic Compound Formulas Example: Ammonium sulfate 1. Write the formulas for the cation and anion, including CHARGES! NH 4 + SO Check to see if charges are balanced. 3. Balance charges, if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Not balanced ( ) 2

17 Writing Ionic Compound Formulas Example: Iron(III) chloride 1. Write the formulas for the cation and anion, including CHARGES! Fe 3+ Cl - 2. Check to see if charges are balanced. 3. Balance charges, if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Not balanced 3

18 Writing Ionic Compound Formulas Example: Aluminum sulfide 1. Write the formulas for the cation and anion, including CHARGES! Al 3+ S Check to see if charges are balanced. 3. Balance charges, if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Not balanced 23

19 Writing Ionic Compound Formulas Example: Magnesium carbonate 1. Write the formulas for the cation and anion, including CHARGES! Mg 2+ CO Check to see if charges are balanced. They are balanced

20 Writing Ionic Compound Formulas Example: Zinc hydroxide 1. Write the formulas for the cation and anion, including CHARGES! Zn 2+ OH - 2. Check to see if charges are balanced. 3. Balance charges, if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Not balanced ( ) 2

21 Writing Ionic Compound Formulas Example: Aluminum phosphate 1. Write the formulas for the cation and anion, including CHARGES! Al 3+ PO Check to see if charges are balanced. They ARE balanced

22 Naming Ionic Compounds  Cation first, then anion  Monatomic cation = name of the element  Ca 2+ = calcium ion  Monatomic anion = root + -ide  Cl − = chloride  CaCl 2 = calcium chloride  Cation first, then anion  Monatomic cation = name of the element  Ca 2+ = calcium ion  Monatomic anion = root + -ide  Cl − = chloride  CaCl 2 = calcium chloride

23 Naming Ionic Compounds  some metal forms more than one cation  use Roman numeral in name  PbCl 2  Pb 2+ is cation  PbCl 2 = lead(II) chloride  some metal forms more than one cation  use Roman numeral in name  PbCl 2  Pb 2+ is cation  PbCl 2 = lead(II) chloride Metals with multiple oxidation states

24 Binary Molecular Compounds  Compounds between two nonmetals  First element in the formula is named first.  Keeps its element name  Gets a prefix if there is a subscript on it  Second element is named second  Use the root of the element name plus the -ide suffix  Always use a prefix on the second element

25 List of Prefixes  1 = mon(o)  2 = di  3 = tri  4 = tetra  5 = penta  6 = hexa  7 = hepta  8 = octa  9 = nona  10 = deka

26 Naming Binary Compounds P2O5 =P2O5 =P2O5 =P2O5 = CO 2 = CO = N 2 O = diphosphorus pentoxide carbon dioxide carbon monoxide dinitrogen monoxide

27 Practice – Write the Formula Compound NameCompound Formula Carbon dioxide Carbon monoxide Diphosphorus pentoxide Dinitrogen monoxide Silicon dioxide Carbon tetrabromide Sulfur dioxide Phosphorus pentabromide Iodine trichloride Nitrogen triiodide Dinitrogen trioxide Check next slide for answers

28 Answers – Write the Formula Compound NameCompound Formula Carbon dioxideCO 2 Carbon monoxideCO Diphosphorus pentoxideP2O5P2O5 Dinitrogen monoxideN2ON2O Silicon dioxideSiO 2 Carbon tetrabromideCBr 4 Sulfur dioxideSO 2 Phosphorus pentabromidePBr 5 Iodine trichlorideICl 3 Nitrogen triiodideNI 3 Dinitrogen trioxideN2O3N2O3

29 Practice – Name the Compounds Compound FormulaCompound Name N2O4N2O4 SO 3 NO NO 2 As 2 O 5 PCl 3 CCl 4 H2OH2O SeF 6 Check next slide for answers

30 Answers – Name the Compounds Compound FormulaCompound Name N2O4N2O4 dinitrogen tetroxide SO 3 sulfur trioxide NOnitrogen monoxide NO 2 nitrogen dioxide As 2 O 5 diarsenic pentoxide PCl 3 phosphorus trichloride CCl 4 carbon tetrachloride H2OH2Odinitrogen monoxide SeF 6 selenium hexafluoride


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