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Valence Electrons, Ions, and Lewis Dot Diagrams

Valence Electrons, Ions, and Lewis Dot Diagrams. Unit 4. Keeping Track of Electrons. The electrons responsible for the chemical properties of atoms are those in the outer energy level. Valence electrons Valence electrons - The s and p electrons in the outer energy level.

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Valence Electrons, Ions, and Lewis Dot Diagrams

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  1. Valence Electrons, Ions, and Lewis Dot Diagrams Unit 4

  2. Keeping Track of Electrons • The electrons responsible for the chemical properties of atoms are those in the outer energy level. • Valence electrons • Valence electrons - The s and p electrons in the outer energy level. • Core electrons -those in the energy levels below.

  3. Keeping Track of Electrons • Atoms in the same column • Have the same outer electron configuration. • Have the same valence electrons. • Easily found by looking up the group number on the periodic table. • Group 2A - Be, Mg, Ca, etc.- • 2 valence electrons

  4. Lewis Dot diagrams • A way of keeping track of valence electrons. • How to write them • Write the symbol. • Put one dot for each valence electron • Don’t pair up until they have to Xe

  5. The Lewis Dot diagram for Nitrogen • Nitrogen has 5 valence electrons. • First we write the symbol. N • Then add 1 electron at a time to each side. • Until they are forced to pair up.

  6. Write the Lewis dot diagram for • Na • Mg • C • O • F • Ne • He

  7. Electron Configurations for Cations • Metals lose electrons to attain noble gas configuration. • They make positive ions. • If we look at electron configuration it makes sense. • Na 1s22s22p63s1 - 1 valence electron • Na+ 1s22s22p6 -noble gas configuration

  8. Electron Dots For Cations • Metals will have few valence electrons Ca

  9. Electron Dots For Cations • Metals will have few valence electrons • These will come off Ca

  10. Electron Dots For Cations • Metals will have few valence electrons • These will come off • Forming positive ions Ca+2

  11. Electron Configurations for Anions • Nonmetals gain electrons to attain noble gas configuration. • They make negative ions. • If we look at electron configuration it makes sense. • S 1s22s22p63s23p4 - 6 valence electrons • S-2 1s22s22p63s23p6 -noble gas configuration.

  12. Electron Dots For Anions • Nonmetals will have many valence .electrons. • They will gain electrons to fill outer shell. P P-3

  13. Stable Electron Configurations • All atoms react to achieve noble gas configuration. • Noble gases have 2 s and 6 p electrons. • 8 valence electrons . • Also called the octet rule. Ar

  14. +1 +2 +3 -3 -2 -1

  15. Unit 4: Chapter 8 Ionic Bonding

  16. +1 +2 +3 -3 -2 -1

  17. Properties of Ionic Compounds • Crystalline structure. • A regular repeating arrangement of ions in the solid. • Ions are strongly bonded. • Structure is rigid. • High melting points- because of strong forces between ions.

  18. Crystalline structure

  19. Ionic Bonding • Anions and cations are held together by opposite charges. • Ionic compounds are called salts. • Simplest ratio is called the formula unit. • The bond is formed through the transfer of electrons. • Electrons are transferred to achieve noble gas configuration.

  20. Do they Conduct? • Conducting electricity is allowing charges to move. • In a solid, the ions are locked in place. • Ionic solids are insulators. • When melted, the ions can move around. • Melted ionic compounds conduct. • First get them to 800ºC. • Dissolved in water they conduct.

  21. + - + - - + - + + - + - - + - + Ionic solids are brittle

  22. - + - + - + - + + - + - - + - + Ionic solids are brittle • Strong Repulsion breaks crystal apart.

  23. Ionic Bonding Na Cl

  24. Ionic Bonding Na+ Cl-

  25. Ionic Bonding • All the electrons must be accounted for! Ca P

  26. Ionic Bonding Ca P

  27. Ionic Bonding Ca+2 P

  28. Ionic Bonding Ca+2 P Ca

  29. Ionic Bonding Ca+2 P-3 Ca

  30. Ionic Bonding Ca+2 P-3 Ca P

  31. Ionic Bonding Ca+2 P-3 Ca+2 P

  32. Ionic Bonding Ca Ca+2 P-3 Ca+2 P

  33. Ionic Bonding Ca Ca+2 P-3 Ca+2 P

  34. Ionic Bonding Ca+2 Ca+2 P-3 Ca+2 P-3

  35. Ionic Bonding Ca3P2 Formula Unit

  36. Naming ions • We will use the systematic way. • Cation- if the charge is always the same (Group A) just write the name of the metal. • Examples • Sodium ion = Na+ • Barium ion = Ba2+ • Silver ion = Ag+ • Zinc ion = Zn2+

  37. Naming Anions • Anions always have the same charge. • Change the element ending to – ide • Examples • Fluorine as an ion= F-1 fluoride • Chlorine as an ion= Cl- chloride • Oxygen as an ion= O2- oxide

  38. Cl-1 N-3 I-1 S-2 Chloride ion Nitride ion Iodide ion Sulfide ion Name these

  39. Oxide ion Fluoride ion Phosphide ion Strontium ion O2- F- P3- Sr2+ Write these

  40. Naming Binary Ionic Compounds • Binary Compounds - 2 elements. • Ionic - a cation and an anion. • To write the names just name the two ions. • Easy with Representative elements (Group A) • NaCl = Na+ Cl- = sodium chloride • MgBr2 = Mg+2 Br- = magnesium bromide

  41. Writing Formulas • The charges have to add up to zero. • Get charges on pieces. • Charges for Cations come from the periodic table. • If it is a transition metal, the charge is the roman numeral • Anions from the periodic table. • Criss- Cross the charges to determine subscripts

  42. The Criss-Cross Rule Write the formula for calcium chloride. • Calcium is Ca+2 • Chloride is Cl-1 • Criss Cross the charges to determine the subscripts Ca+2 Cl-1 ( only the numbers, not the signs) ANSWER: CaCl2

  43. Naming ions with Transition Metals • Transition metals can have more than one type of charge. • Indicate the charge with roman numerals in parenthesis. • Examples • Ni+2 = nickel (II) ion • Ni+ = nickel (I) ion

  44. Naming Binary Ionic Compounds Write the formulas for each the following • CrN • Sc3P2 • PbO • PbO2 Chromium (III) nitride Scandium (II) phosphide Lead (II) oxide Lead (IV) oxide

  45. Naming Binary Ionic Compounds with Transition Metals • The problem comes with the transition metals. • Need to figure out their charges. • The compound must be neutral. • same number of + and – charges. • Use the anion to determine the charge on the positive ion.

  46. Naming Binary Ionic Compounds • Write the name of CuO • Need the charge of Cu • O is -2 • copper must be +2 • ANSWER: Copper (II) oxide

  47. Name CoCl3 • Cl is -1 • there are three of them = -3 • Co must be +3 • ANSWER: Cobalt (III) chloride

  48. Naming Binary Ionic Compounds • Write the name of Cu2S. • Since S is -2, the Cu2 must be +2, so each one is +1. • ANSWER: copper (I) sulfide • Fe2O3 • Each O is -2 3 x -2 = -6 • 2 Fe must = +6, so each is +3. • ANSWER: iron (III) oxide

  49. Write the formulas for these • Li2S • SnO • SnO2 • MgF2 • FeP • Fe2P3 • Lithium sulfide • tin (II) oxide • tin (IV) oxide • Magnesium fluoride • Iron (III) phosphide • Iron (III) sulfide

  50. Polyatomic ions • Groups of atoms that stay together and have a charge. • You must memorize these by the midterm • Nitrate NO3-1 • Hydroxide OH-1 • Sulfate SO4-2 • Phosphate PO4-3 • Ammonium NH4+1

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