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Elements and Ionic Compounds

Unit II: Intro to Formulas. Elements and Ionic Compounds. A. Element OR Compound?. Elements: Formulas only contain ONE symbol Which means only ONE capital letter. Names are only ONE word long. Compounds: Formulas contain two or more symbols. Which means more than one capital letter.

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Elements and Ionic Compounds

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  1. Unit II: Intro to Formulas Elements andIonic Compounds LPChem1415

  2. A. Element OR Compound? Elements: • Formulas only contain ONE symbol • Which means only ONE capital letter. • Names are only ONE word long. Compounds: • Formulas contain two or more symbols. • Which means more than one capital letter. • Names are TWO words long. LPChem1415

  3. Elements: A Review We already learned that: • Most element formulas consist of the element symbol and nothing more. • (Al, Cu, Ne, Au, etc.) • Seven elements are “diatomic” and always pair up in the elemental state: • (H2, N2, O2, F2, Cl2, Br2, I2) • Elements go by their own names • But sometimes Carbon is sneaky. LPChem1415

  4. Compounds • There are different types of chemical compound. For this unit, we are only learning IONIC compounds: • Ionic compounds form by transfer of valence electrons. • Valence electrons are the outermost electrons in an atom. • This atom has lots of electrons. But only ONE in its VALENCE. LPChem1415

  5. The periodic table • The table is organized so similar elements are together. • Similar properties are usually due to similar # of valence electrons. LPChem1415

  6. Groups of similar elements have special names: LPChem1415

  7. # valence electrons increases, left to right: 1 2 345678 LPChem1415

  8. Sodium has 1 valence electron • Chlorine has 7 valence electrons 1 2 345678 LPChem1415

  9. Lewis Dot Structures • Show ONLY valence electrons • Each electron is shown as a dot. • Electrons come in pairs– top, bottom, left, & rightof symbol. LPChem1415

  10. Valence Electrons & Stability • Eight valence electrons = a “full octet” • Atoms with a full octet are the most stable • This is why the noble gases are “noble” 12 345678 LPChem1415

  11. Valence Electrons & Stability • All other elements work to achieve a “full octet” by gaining, losing, or sharing electrons: Atoms are like onions– the electrons come in layers. The sodium now has zero electrons in the diagram, but there was already a full octet in the next lower layer, so it is stable now. LPChem1415

  12. Valence Electrons & Stability • Gaining or losing electrons gives the atom a charge. • Charged particles are called IONS. • If one atom loses electrons, another must gain them. • Even tiny electrons are matter, and can’t be created or destroyed! LPChem1415

  13. Valence Electrons & Stability • An atom that loses electrons becomes positively charged. • This is a cation. (Subtracting a negative makes a positive!) LPChem1415

  14. Cations are Positive LPChem1415

  15. Valence Electrons & Stability • An atom that gains electrons becomes negatively charged. • This is an anion. Note: the name changes to the “–ide” form when it becomes negative! LPChem1415

  16. Barium is in column 2 and has 2 valence electrons • Sulfur is in column 16 and has 6 valence electrons 1 2 3 4 5 6 7 8 LPChem1415

  17. To get full octets: • Barium must lose TWO electrons • Sulfur must gain TWO electrons • Key Point: Ion charge is based on how many electrons must be gained or lost to get a full octet. LPChem1415

  18. Valence Electrons & Stability Main Group Ion Charges 1+ 0 2+ 3+ 4± 3- 2- 1- LPChem1415

  19. Ionic Compounds Form because opposite charged ions attract each other. • Cations and anions arrange themselves in a “crystal lattice.” LPChem14

  20. Ionic Crystals • A “crystal lattice” • Is a 3-D grid of ions– the general structure of ionic compounds • Is hard to melt due to attraction between anions and cations LPChem1415

  21. C. Ionic Nomenclature Ionic Names: Cations • Write the name of the cationfirst. • Stock System: Use Romannumerals to show the cation’s charge if more than one is possible. • D-block (transition metals) • Poor metals LPChem1415

  22. C. Ionic Nomenclature • How do you know the Roman numeral? Math! (The overall charge must equal zero.) • FeCl2 • Cl gets a charge of: 1- (because it is in column 17) • Fe must have a charge of ____ to make the compound = 0 2+ • This is Iron (II) Chloride LPChem1415

  23. C. Ionic Nomenclature • Fe2 S3 • There are only two capital letters, so no polyatomic ion to worry about. • I look up S on the periodic table • Column 16: • 6 valence electrons, 2- charge S LPChem1415

  24. C. Ionic Nomenclature • Fe2 S3 = iron ( ? ) sulfide 6- ( ) 3 = 0 6+ ( )2 + 2- 3+ Fe2 S3 Iron (III) sulfide LPChem1415

  25. C. Ionic Nomenclature • Fe2 (CO3)3 = iron ( ? ) carbonate 6+ ( )2 + 6- ( ) 3 = 0 2- 3+ Fe2 (CO3)3 Iron (III) carbonate LPChem1415

  26. C. Ionic Nomenclature • Fe CO3 = iron ( ? ) carbonate 2+ ( )1 + 2- ( ) 1 = 0 2- 2+ Fe CO3 Iron (II) carbonate LPChem1415

  27. C. Ionic Nomenclature • Ni2 CO3 = nickel ( ? ) carbonate 2+ ( )2 + 2- ( ) 1 = 0 2- 1+ Ni2 CO3 Nickel (I) carbonate LPChem1415

  28. C. Ionic Nomenclature Ionic Names: Cations • Roman numerals are NOT needed for: • Group 1 & 2 • (1+, 2+) • Ag, Zn, Al LPChem1415

  29. C. Ionic Nomenclature Ionic Names: Anions • Monatomic anion names are the first syllable of the element name, then -ide. • (Chloride, oxide, phosphide, nitride, etc) • Polyatomic ions have special names. (Chart on the back of your periodic table.) • Do NOT change the ending of polyatomic ions. LPChem1415

  30. C. Ionic Nomenclature Overview: • Consider the following: • Does it contain a polyatomic ion? • 2 elements  no; ending is “-ide” • 3+ elements  yes; ending is -ate -ite • Does it contain a Roman numeral? • Check the table: is the metal NOT in Groups 1 or 2 (or Ag, Zn, Al)? • NO numerical prefixes! LPChem1415

  31. C. Ionic Nomenclature • NaBr • Na2CO3 • FeCl3 • sodium bromide • sodium carbonate • iron(III) chloride LPChem1415

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