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“Chemical Names and Formulas” – Part I

“Chemical Names and Formulas” – Part I

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“Chemical Names and Formulas” – Part I

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  1. H2O “Chemical Names and Formulas” – Part I

  2. Atoms and Ions • Atoms are electrically neutral. • Because there is the same number of protons (+) and electrons (-). • Ions are atoms, or groups of atoms, with a charge (positive or negative) • They have different numbers of protons and electrons. • Only electrons can move, and ions are made by gaining or losing electrons.

  3. An Anion is… • A negative ion. • Has gained electrons. • Nonmetals can gain electrons. • Charge is written as a superscript on the right. Has gained one electron (-ide is new ending = fluoride) F1- O2- Gained two electrons (oxide)

  4. A Cation is… • A positive ion. • Formed by losing electrons. • More protons than electrons. • Metals can lose electrons Has lost one electron (no name change for positive ions) K1+ Ca2+ Has lost two electrons

  5. Oxidation Numbers • Number given to an element to show how many electrons it has lost, gained or shared when forming a compound • Ex: NaCl • To form this compound: • Na lost 1 e-, Cl gained 1 e-

  6. Assigning Oxidation Numbers • Rule #1 For Groups 1A – 4A: Take number before “A” and add (+) in front • Na in group 1A = +1 O.N. • Rule #2 For Groups 5A-8A: Take number before “A” and subtract 8 from it • Cl in group 7A = 7-8 = -1 O.N.

  7. Oxidation numbers for transition metals (Groups 3-12) • Transition metals have multiple oxidation states • Cu +1 Cu +2 • Fe+2, Fe +3 • Pb +2, Pb +4

  8. Writing Chemical formulas • Write symbol of element with (+) oxidation number first • Write symbol of element with (-) oxidation number Ex. Na+1 Cl -1

  9. Writing Chemical Formulas • If Numbers add up to zero cross out charges and write together Na+1 Cl -1 = NaCl Ca +2 O -2= CaO

  10. Writing Chemical Formulas • If oxidation numbers don’t add up to zero criss-cross the numbers (Al and S) • Al +3S-2 = Al2S3

  11. Predicting Ionic Charges Group 1A: Lose 1 electron to form 1+ ions K1+ H1+ Li1+ Na1+ Rb1+

  12. Predicting Ionic Charges Group 2A: Loses 2 electrons to form 2+ ions Be2+ Mg2+ Ca2+ Sr2+ Ba2+

  13. Predicting Ionic Charges Group 3A: Loses 3 electrons to form 3+ ions B3+ Al3+ Ga3+

  14. Predicting Ionic Charges Group 4A: Neither! Group 4A elements rarely form ions (they tend to share) Do they lose 4 electrons or gain 4 electrons?

  15. Predicting Ionic Charges N3- Nitride Group 5A: Gains 3 electrons to form 3- ions P3- Phosphide As3- Arsenide

  16. Predicting Ionic Charges O2- Oxide Group 6A: Gains 2 electrons to form 2- ions S2- Sulfide Se2- Selenide

  17. Predicting Ionic Charges Group 7A: Gains 1 electron to form 1- ions F1- Fluoride Br1- Bromide Cl1- Chloride I1- Iodide

  18. Predicting Ionic Charges Stable noble gases do not form ions! Group 8A:

  19. Predicting Ionic Charges Group B elements: Many transition elements have more than one possible oxidation state. Note the use of Roman numerals to show charges Iron (II) = Fe2+ Iron (III) = Fe3+

  20. Practice • barium sulfide • NaF • iron (III) oxide • Mn2O5

  21. Practice • barium sulfide - BaS • NaF – sodium fluoride • iron (III) oxide – Fe2O3 • Mn2O5 - manganese (V) oxide

  22. “Chemical Names and Formulas” – Part II

  23. Naming cations • Two methods can clarify when more than one charge is possible: • Stock system – uses roman numeralsin parenthesis to indicate the numerical value • Classical method– uses root word with suffixes (-ous, -ic) • Does not give true value

  24. Naming cations • We will use the Stock system. • Cation - if the charge is always the same (like in the Group A metals) just write the name of the metal. • Transition metals can have more than one type of charge. • Indicate their charge as a roman numeral in parenthesis after the name of the metal

  25. Examples: • (Sodium…Group IA) = Na1+ • (Calcium…Group IIA) = Ca2+ • (Iron (III)…Transition Element) = Fe3+ • (Iron (II)…Transition Element) = Fe2+

  26. Examples: • Potassium ion = K1+ • Magnesium ion = Mg2+ • Copper (II) ion = Cu2+

  27. Naming Anions • Anions are always the same charge • Change the monatomic element ending to – ide • F1- a Fluorine atom will become a Fluoride ion.

  28. Examples: • Chloride = Cl1- • Nitride = N3- • Bromide = Br1-

  29. Examples: • Sulfide ion = S2- • Iodide ion = I1- • Phosphide ion = P3-

  30. Polyatomic ions are… • Groups of atoms that stay together and have an overall charge, and one name. • Usually end in –ate or -ite • Acetate: C2H3O21- • Nitrate: NO31- • Nitrite: NO21- • Permanganate: MnO41- • Hydroxide: OH1- *metal + polyatomic ion = an ionic compound (just like metal + nonmetal)

  31. If the polyatomic ion begins with H, combine the word hydrogen with the other polyatomic ion present… Ex. H1+ + CO32- → HCO31- hydrogen + carbonate → hydrogen carbonate ion

  32. Things to look for: • If cations have ( ), the number in parenthesis is their charge. • If anions end in -ide they are probably off the periodic table (Monoatomic) • If anion ends in -ate or –ite, then it is polyatomic

  33. Binary Ionic Compounds • Contain 2 different elements • Name the metal first, then the nonmetal as -ide. • Use name of a metal with a fixed charge Groups 1A, 2A, 3A and Ag, Zn, and Cd Examples: NaCl sodium chloride ZnI2 zinc iodide Al2O3 aluminum oxide

  34. Naming Binary Covalent Compounds (Molecular Compounds) Two nonmetals • Name each element • End the last element in -ide • Add prefixes to show more than 1 atom

  35. Molecular compounds are… • made of just nonmetals • smallest piece is a molecule • can’t be held together by opposite charge attraction • can’t use charges to figure out how many of each atom (there are no charges present)

  36. Molecular compounds are easier! • Ionic compounds use charges to determine how many of each. • You have to figure out charges. • May need to criss-cross numbers. • Molecular compounds: the name tells you the number of atoms. • Uses prefixes to tell you the exact number of each element present!

  37. Prefixes • 1 = mono- • 2 = di- • 3 = tri- • 4 = tetra- • 5 = penta- • 6 = hexa- • 7 = hepta- • 8 = octa- *KNOW THESE!! • 9 = nona- • 10 = deca-

  38. Prefixes • To write the name, write two words: • One exception is we don’t write mono if there is only one of the first element. • Normally, we do not have double vowels when writing names (oa oo) name Prefix Prefix -ide name

  39. Examples: = dinitrogen monoxide(also called nitrous oxide or laughing gas) • N2O • NO2 • Cl2O7 • CBr4 • CO2 • BaCl2 = nitrogen dioxide = dichlorine heptoxide = carbon tetrabromide = carbon dioxide (This one will not use prefixes, since it is an ionic compound!)

  40. Examples: • diphosphorus pentoxide = P2O5 • sulfur hexafluoride = ?

  41. Naming Ternary Compounds • Contain at least 3 elements • Name the nonmetals as a polyatomic ion • Examples: NaNO3 Sodium nitrate K2SO4Potassium sulfate Al(HCO3)3Aluminumbicarbonate oraluminumhydrogen carbonate

  42. Practice… • lithium oxide • dinitrogen trioxide • Si2Br6 • aluminum carbonate

  43. Practice… • lithium oxide – Li2O • dinitrogen trioxide – N2O3 • Si2Br6 – disilicon hexabromide • aluminum carbonate – Al2(CO3)3

  44. “Chemical Names and Formulas” – Part III

  45. Acids are… • Compounds that give off hydrogen ions (H1+) when dissolved in water • Will start the formula with H. • There will always be some Hydrogen next to an anion. • The anion determines the name.

  46. Rules for Naming acids: • If the anion attached to hydrogen ends in -ide, put the prefix hydro- and change -ide to -ic acid • HCl - hydrogen ion and chloride ion = hydrochloric acid • H2S hydrogen ion and sulfide ion = hydrosulfuric acid

  47. Naming Acids • If the anion has oxygen in it, then it ends in -ate or -ite • change the suffix -ateto -ic acid(use no prefix) • Example: HNO3 Hydrogen and nitrate ions = Nitric acid • change the suffix -iteto -ous acid(use no prefix) • Example: HNO2 Hydrogen and nitrite ions = Nitrous acid

  48. Normal ending ____-ide ____-ate ____-ite Acid name is… hydro-___-ic acid _____-ic acid _____-ous acid Naming Acids

  49. Examples: • HF = hydrofluoric acid • H2SO4 = sulfuric acid • H2SO3 = sulfurous acid

  50. Writing Acid Formulas – in reverse! • Hydrogen will be listed first • The name will tell you the anion • Be sure the charges cancel out. • -ate anioncomes from –ic ending • -ite anion comes from –ous ending