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6.4 Writing formulas for ionic compounds

6.4 Writing formulas for ionic compounds. ide. The names of all ionic compounds which are made of two elements always end in – ide NaCl is sodium chlor ide CaCL 2 is calcium chlor ide AlCl 3 is aluminum chlor ide. Binary ionic compounds.

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6.4 Writing formulas for ionic compounds

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  1. 6.4 Writing formulas for ionic compounds

  2. ide • The names of all ionic compounds which are made of two elements always end in –ide • NaCl is sodium chloride • CaCL2 is calcium chloride • AlCl3 is aluminum chloride

  3. Binary ionic compounds • Compounds composed of two elements are called binary compounds • Compounds composed of a metal and a non-metal are called ionic compounds: • NaCl • CaF2 • K2 S So these are all binary ionic compounds!

  4. One metal ion from over here and one non-metal ion from over here make up a binary ionic compound

  5. Balancing the charges • When writing the formula for any binary ionic compound, the chargeof the cation(s)must equal the charge of the anion(s) • Using the periodic chart, the charges of the ions formed from elements in Group A are easily determined

  6. Remember where the Group A elements are? -1 +3 -3 -2 +1 +2

  7. Calcium bromide • Calcium is in Group 2A, so it loses two electrons and becomes Ca+2 • Bromine is in Group 7A, so it gains an electron and becomes Br- • To balance the charges when these two ions form an ionic compound, we must have two bromines for each calcium • We write this as CaBr2 • Binary ionic compounds end in “ide”

  8. Balance these binary ionic formulas • Na + O • Mg + S • Ca + F • Al + Br • Ba + O

  9. Criss-cross method • If you know the charges of the two ions, you can use the charge of the first ion as the subscript of the second, and vice versa: Fe+3 and O-2 Fe+3 O-2 Fe2O3

  10. Namingionic compounds • What if you want to write the name of the formula instead? • You will need to include all the information that the formula does • This is easy for binary ionic compounds involving Group A ions • NaCl is sodium chloride • MgBr2 is magnesium bromide

  11. When writing the names of ionic compounds involving transitionelements (Group B), it is necessary to look at the anionto determine the charge of the cation. (transition or Group B elements can have several oxidation states)

  12. Remember where the Group B elements are?

  13. copper oxide can mean either CuO or Cu2O, depending on which copper cation is involved. Since we know the oxygen ion always has a charge of -2, we also must include the +2 charge when writing the namefor CuO, and the +1 charge when writing the name for Cu2O. CuO is written copper(II) oxide Cu2O is written copper(I) oxide

  14. Since oxygen always has a charge of -2, if you were writing the name for SnO2,you must assume that Sn (tin) has a charge of +4 because of the two oxygens in the formula. Therefore, the correctly written nameof the substance is tin(IV) oxide

  15. Write the names of these formulas • Fe2O3 • Ni2O3 • MnO2 • Cu2S • FeCl3

  16. Ternary ionic compounds Ternary compounds are compounds which contain three different elements. Ternary ionic compounds usually contain a polyatomic ion. Remember, polyatomic ions are treated as a unit and have a specific charge.

  17. Ternary ionic compounds(three elements) • Use the same method (criss-cross) of balancing a ternary compound as you would a binary compound • K+1 and (SO4)-2 • K+1 (SO4)-2 K2SO4

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