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Unit 6: Writing and Naming Chemical Formulas

Unit 6: Writing and Naming Chemical Formulas

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Unit 6: Writing and Naming Chemical Formulas

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  1. Unit 6:Writing and Naming Chemical Formulas Chemistry I 2013-2014

  2. Ions & The Octet Rule

  3. Ion – an atom or bonded group of atoms with a positive or negative charge Anion – a negatively charged ion Cation – a positively charged ion Octet Rule – “atoms lose, gain, or share electrons in order to acquire the stable electron configuration of a noble gas” Vocabulary

  4. An ion is an atom or group of atoms that has either a positive or negative charge Ion

  5. Atoms gain or lose electrons to become stable An atom is stable when the valence shell is full Atoms form ions by gaining or losing electrons

  6. Sodium loses one electron to become stable Results in an ion that has a positive charge Cations – Positive Ions

  7. The symbol “+” is written as a superscript to indicate that the sodium has a charge of 1+ Cations Na+

  8. Chlorine gains one electron to become stable Results in an ion with a negative charge Anions – Negative Ions

  9. The symbol “-” is written as a superscript to indicate that the chlorine ion has a charge of 1- Anion Cl-

  10. Both ions have a full valence shell containing the maximum number of electrons possible (8) This new arrangement of valence electrons has less energy than the previous arrangement and is stable The Octet Rule Na+ Cl-

  11. A metal atom that has lost electrons (cation) and a nonmetal atom that has gained electrons (anion) will have the same number of electrons as its nearest noble gas. Noble Gases

  12. Common Charges

  13. Cations: A metal that has lost electrons to become an ion has the same name as the element Ca2+ = calcium ion Anions: A nonmetal that has gained electrons to become an ion has the same name as the element but with the ending changed to –ide S2- = sulfide ion Nitrogen  Nitride Phosphorous  Phosphide Oxygen  Oxide Flourine  Flouride Naming Ions

  14. Multivents – an element that can form an ion in more than one way Naming: Always include the ion charge as Roman numerals in brackets Cu+ copper (I) “copper one” Cu2+ copper (II) “copper two” Roman Numerals for Multivents

  15. Scandium column: always +3, no Roman numeral needed F-block: always +3, no Roman numeral needed Ag: always +1, no Roman numeral needed Cd & Zn: always +2, no Roman numeral needed Sn & Pb: either +2 or +4 Transition Metals to Know

  16. An oxidation number is the positive or negative charge of an ion Element Oxidation # Li +1 Be +2 O -2 F -1 Charges  Oxidation Number

  17. Polyatomic Ions

  18. Writing and Naming Ionic Compounds

  19. Cation + anion Name the cation first (typically a metal) just as it appears on the periodic table Na+ = Sodium Ca+2 = Calcium Ionic Compounds

  20. Write the anion next (typically a nonmetal) Change the ending to –ide **If the anion is a polyatomic ion, the name stays the same** Ionic Compounds

  21. NaCl Sodium Chloride AlCl3 Aluminum Chloride Na2O Sodium Oxide Al2O3 Aluminum Oxide Practice

  22. Identify the metal as a Transition with multiple oxidation numbers (ex. Fe) Uncross the “criss-cross” If nothing to uncross, identify the charge of the anion. The charges have been simplified Transition metals will be the same just + How to determine the Oxidation Number of Transition Metals +3 -2 Fe2O3 Iron (III) Oxide +2 -2 FeS Iron (II) Sulfide

  23. CuO Name: Copper (II) Oxide Practice

  24. Writing Ionic Formula • Identify the ions and their charges • Criss-Cross the charges • The sum of the oxidation numbers must equal zero, so by writing the subscripts we are able to balance the charge • Example: Calcium Chloride • Ions: Ca+2 and Cl-1 +2 -1 CaCl • Formula = CaCl2 • (Don’t write 1’s)

  25. Practice • Magnesium Oxide • Copper (I) Phosphide • Mg2O2 **Simplify to MgO • Cu3P

  26. You can’t change the subscripts in Polyatomic Ions Put the Polyatomic Ion in brackets and place the subscripts outside those Calcium Phosphate Ca+2 PO43- Ca3(PO4)2 Polyatomic Ions

  27. Naming Covalent Compounds

  28. Ionic compounds have a metal and a nonmetal, a cation and an anion Covalent compounds are called molecules They are made from elements that are similar in electronegativity What’s the difference between covalent and ionic?

  29. Covalent Naming uses Prefixes • Mono • Di • Tri • Tetra • Penta • Hexa • Hepta • Octa • Nona • deca

  30. Rules • If you have more than one atom of that element in the compound, you will need a prefix before it’s name. • Always put a prefix before the name of the second element • Change the ending of the second element to -ide • P2O5 • Diphosphorouspentoxide • CO • Carbon monoxide

  31. Practice • OF2 • SO2 • SO3 • N2O5 • N2O4 • H2O • Oxygen diflouride • Sulfur dioxide • Sulfur trioxide • Dinitrogenpentoxide • Dinitrogen tetroxide • Dihydrogen monoxide

  32. Names and Formulas of Common Acids and Bases

  33. Acids are almost always compounds made from hydrogen and an anion • Hydrogen + Halogen = hydro________ic acid • HCl = hydrochloric acid • Hydrogen + Polyatomic ion –ate = _______ic acid • HNO3 = nitric acid • Hydrogen + Polyatomic ion –ite = _______ous acid • H2SO3= sulfurous acid Naming Acids

  34. Bases are almost always compounds made from hydroxide (HO-) and a cation Cation + Hydroxide Mg(OH)2 = Magnesium Hydroxide LiOH = Lithium Hydroxide Naming Bases

  35. Practice • Hydroiodic acid • HBr • H2CO3 • Lead (II) Hydroxide • Sn(OH)4 • Zn(OH)2 • HI • Hydrobromic Acid • Carbonic Acid • Pb(OH)2 • Stannic Hydroxide • Zinc Hydroxide

  36. Empirical and Molecular Formulas

  37. The formula that gives the simplest whole number ration of atoms in a compound Molecular Formula: C6H12O6 Empirical Formula: CH2O Empirical Formula

  38. What is the empirical formula of…? • C6H12O6 • Fe3O2 • C6H10O4 • CH2O • Fe3O2 • C3H5O2