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Molecules and Ions Image courtesy of www.lab-initio.com.

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

1

2 Molecules and Ions Image courtesy of

3 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

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

5 Ions   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).

6 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 +

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

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

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

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

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

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

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

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

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

16 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

17 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

18 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

19 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

20 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

21 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

22 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

23 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

24 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

25 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

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

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

28 Practice – Write the Formula Check next slide for answers

29 Answers – Write the Formula

30 Practice – Name the Compounds Check next slide for answers

31 Answers – Name the Compounds


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