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Elements and Ionic Compounds in Chemistry

Learn about elements with singular symbols and compounds with multiple symbols, along with the formation of ionic compounds by electron transfer. Valence electrons, Lewis dot structures, and stability are explored using examples. Ionic naming conventions are discussed with examples of cations and anions. Discover how opposite charged ions attract in ionic crystals.

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Elements and Ionic Compounds in Chemistry

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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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