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Unit 4

Unit 4. Naming Compounds Writing Formulas. Compounds. Compounds = composed of 2 or more elements chemically combined Properties completely different from component elements Salt Sodium (Na) – shiny, reactive, poisonous Chlorine (Cl) – pale yellow gas, reactive, poisonous

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Unit 4

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  1. Unit 4 Naming Compounds Writing Formulas

  2. Compounds • Compounds = composed of 2 or more elements chemically combined • Properties completely different from component elements • Salt • Sodium (Na) – shiny, reactive, poisonous • Chlorine (Cl) – pale yellow gas, reactive, poisonous • Sodium chloride (NaCl) – table salt, flavor enhancer

  3. Chemical Formulas represent compounds.

  4. Formulas Describe Compounds Examples: water = H2O \ two atoms of hydrogen and 1 atom of oxygen table sugar (sucrose) = C12H22O11\12 atoms of C, 22 atoms of H and 11 atoms O

  5. Classifying Materials • Covalent compounds = compounds whose particles are molecules made of only nonmetals, i.e. CO2 • Ionic compounds = compounds whose particles are cations (+) and anions (-), i.e. NaCl Tro's Introductory Chemistry, Chapter 5

  6. Two Types of Compounds Ionic Covalent Smallest piece Formula Unit Molecule Types of elements Metal and Nonmetal Nonmetals Solid, liquid or gas State solid Melting Point High >300ºC Low <300ºC

  7. IONIC COMPOUNDS • composed of positive and negative ions. • usually formed from a metal and non-metal. • these elements arenot attached to one another.

  8. ions • Atoms are electrically neutral and usually have the same number of protons and electrons. • Ions are atoms, or groups of atoms, with a charge. • Different numbers of protons and electrons. • Only electrons can move. • Gain or lose electrons.

  9. Anion • Anegative ion. • Has gained electrons. • Non metals can gain electrons. • Charge is written as a superscript on the right. F1- Has gained one electron O2- Has gained two electrons

  10. Cations • Positive ions. • Formed by losing electrons. • More protons than electrons. • Metals form cations. K1+ Has lost one electron Ca2+ Has lost two electrons

  11. Formula Unit • The smallest whole number ratio of atoms in an ionic compound.

  12. Charges on ions • For most of Group A elements, location on the Periodic Table can tell what kind of ion they form • Elements in the same group have similar properties. • Including the charge when they are ions.

  13. Representative elements 1A 0 5A 7A 2A 3A 4A • The group A elements • The tall columns 6A

  14. Representative elements 1A 0 5A 7A 2A 3A 4A • We used them to count valence electrons 6A

  15. Charge in groups 1A, 2A and 3A is the group number 1+ in 5A, 6A and 7A is 8 - the group # and is negative 2+ 3+ 3- 2- 1-

  16. The charge is the is the oxidation number 1+ 2+ 3+ 3- 2- 1-

  17. Naming Binary Ionic Compounds • Contain Metal Cation + Nonmetal Anion • Metal listed first in formula & name • name metal cation first, name nonmetal anion second • cation name is the metal name • nonmetal anion named by changing the ending on the nonmetal name to -ide

  18. Naming ions • Most transition metals can have more than one type of charge. • Indicate the charge with Roman numerals in parenthesis. • Co2+ Cobalt(II) ion

  19. Name these • Na1+ Sodium ion • Ca2+ Calcium ion • Al3+ Aluminum ion • Fe3+ Iron(III) ion • Fe2+ Iron(II) ion • Pb2+ Lead(II) ion • Li1+ Lithium ion

  20. Naming Anions • Anions are always the same. • Change the element ending to – ide • F1- Fluorine

  21. Naming Anions • Anions are always the same • Change the element ending to – ide • F1- Fluoride ion

  22. Name these • Cl1- Chloride ion • N3- Nitride ion • Br1- Bromide ion Oxide ion • O2- Gallium ion • Ga3+

  23. Polyatomic Ions Definition •tightly bound groups of atoms that behave as a unit and carry a charge. Example SO32-, NO2-, ClO2-

  24. Some Common Polyatomic Ions(be able to recognize these)

  25. Ionic Compound Formulas

  26. Subscripts, small numbers to the lower right of the chemical symbol, represent the number of that element present in the compound. The subscript of 1 is never written in a chemical formula. It is understood since the chemical symbol is there. Add subscripts after a chemical symbol, when needed, to make the oxidation numbers total zero. H2O

  27. So how do we use the periodic table to write formulas?Here are a few simple steps to follow in going from a compound’s name to its formula:-

  28. So how do we use this table?Here are a few simple steps to follow in going from a compound’s name to its formula:-I’ll use calcium chloride as a example

  29. So how do we use this table?Here are a few simple steps to follow in going from a compound’s name to its formula:-I’ll use calcium chloride as a example1 write the symbols implied by the name

  30. So how do we use this table?Here are a few simple steps to follow in going from a compound’s name to its formula:-I’ll use calcium chloride as a example1 write the symbols implied by the nameCa and Cl

  31. So how do we use this table?Here are a few simple steps to follow in going from a compound’s name to its formula:-I’ll use calcium chloride as a example1 write the symbols implied by the nameCa and Cl (compounds of two elements usually have a name ending in –ide, for three elements it’s usually -ate)

  32. So how do we use this table?Here are a few simple steps to follow in going from a compound’s name to its formula:-I’ll use calcium chloride as a example1 write the symbols implied by the nameCa and Cl(compounds of two elements usually have a name ending in –ide, for three elements it’s usually -ate)2 Find the numbers on the periodic table

  33. So how do we use this table?Here are a few simple steps to follow in going from a compound’s name to its formula:-I’ll use calcium chloride as a example1 write the symbols implied by the nameCa and Cl(compounds of two elements usually have a name ending in –ide, for three elements it’s usually -ate)2 Find the numbers on the periodic tableCa+2 and Cl-1

  34. So how do we use this table?Here are a few simple steps to follow in going from a compound’s name to its formula:-I’ll use calcium chloride as a example1 write the symbols implied by the name Ca and Cl (compounds of two elements usually have a name ending in –ide, for three elements it’s usually -ate)2 Find the numbers on the list Ca +2 and Cl -13 The rule now is that “The numbers in the compound must add to zero”.

  35. So how do we use this table?Here are a few simple steps to follow in going from a compound’s name to its formula:-I’ll use calcium chloride as a example1 write the symbols implied by the nameCa and Cl (compounds of two elements usually have a name ending in –ide, for three elements it’s usually -ate)2 Find the numbers on the listCa+2 and Cl-13 The rule now is that “The numbers in the compound must add to zero”. one Ca (+2) and two Cl (-1) will add to 0.

  36. So how do we use this table?Here are a few simple steps to follow in going from a compound’s name to its formula:-I’ll use calcium chloride as a example1 write the symbols implied by the nameCa and Cl(compounds of two elements usually have a name ending in –ide, for three elements it’s usually -ate)2 Find the numbers on the listCa+2 and Cl-13 The rule now is that “The numbers in the compound must add to zero”. one Ca (+2) and two Cl (-1) will add to 0.4 and so the formula isCaCl2

  37. 2 Now let’s try aluminium iodide1 Al and I

  38. 2 Now let’s try aluminium iodide1 Al and I2 Al +3 and I -1

  39. 2 Now let’s try aluminium iodide1 Al and I2 Al +3 and I -13 one Al will need 3 I

  40. 2 Now let’s try aluminium iodide1 Al and I2 Al +3 and I -13 one Al will need 3 I4 formula is AlI3

  41. 2 Now let’s try aluminium iodide1 Al and I2 Al +3 and I -13 one Al will need 3 I4 formula is AlI33 sodium oxide

  42. 2 Now let’s try aluminium iodide1 Al and I2 Al +3 and I -13 one Al will need 3 I4 formula is AlI33 sodium oxide1 Na and O

  43. 2 Now let’s try aluminium iodide1 Al and I2 Al +3 and I -13 one Al will need 3 I4 formula is AlI33 sodium oxide1 Na and O2 Na +1 and O -2

  44. 2 Now let’s try aluminium iodide1 Al and I2 Al +3 and I -13 one Al will need 3 I4 formula is AlI33 sodium oxide1 Na and O2 Na +1 and O -23 this time we need two Na for one O

  45. 2 Now let’s try aluminium iodide 1 Al and I 2 Al +3 and I -1 3 one Al will need 3 I 4 formula is AlI33 sodium oxide 1 Na and O 2 Na +1 and O -2 3 this time we need two Na for one O 4 formula is Na2O

  46. 2 Now let’s try aluminium iodide1 Al and I2 Al +3 and I -13 one Al will need 3 I4 formula is AlI33 sodium oxide1 Na and O2 Na +1 and O -23 this time we need two Na for one O4 formula is Na2Onotice that in the name and the formula, the metal or hydrogen (things which have the positive numbers) come first.

  47. The easiest way to think of writing chemical formulas is to use the oxidation number (without the + or -) of one element as the subscript of the other element. +2 -1 Ca Cl

  48. Cross over the oxidation numbers without the charges!!! +2 -1 Ca Cl

  49. Ca Cl 2 REMINDER: DO NOT write a subscript of 1. Reduce the subscripts if needed.

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