Forming Ionic Compounds Adrena McDonald Venture Alternative High School

Before We Begin Cut out the ions from your student worksheets. Have a glue stick ready to attach the ions to your compound worksheet. Now, lets do the first few together.

Cl -1 B +3 1.Boron (B +3 ) + Chlorine (Cl -1 ) 1 boron atom for every 3 chlorine atoms 1. BCl 3 boron chloride BCl 3

2. Magnesium (Mg +2 ) + Chlorine (Cl -1 ) 1 magnesium atom for every 2 chlorine atoms 2. MgCl 2 magnesium chloride MgCl 2 Mg +2 Cl -1

3. Sodium (Na +1 ) + Chlorine (Cl -1 ) 1 sodium atom for every 1 chlorine atom 3. NaCl sodium chloride NaCl Na +1 Cl -1

4. Calcium (Ca +2 ) + Sulfur (S -2 ) 1 calcium atom for every 1 sulfur atom 4. CaS calcium sulfide CaS Ca +2 S -2

5. Aluminum (Al +3 ) + Nitrogen (N -3 ) 1 aluminum atom for every 1 nitrogen atom 5. AlN aluminum nitride AlN Al +3 N -3

Now, its your turn. Do the remaining questions on your own.

6. Calcium (Ca +2 ) + Bromine (Br -1 ) 1 calcium atom for every 2 bromine atoms 6. CaBr 2 calcium bromide CaBr 2 Ca +2 Br -1

7. Potassium (K +1 ) + Chlorine (Cl -1 ) 1 potassium atom for every 1 chlorine atom 7. KCl potassium chloride KCl K +1 Cl -1

O -2 B Boron (B +3 ) + Oxygen (O -2 ) 2 boron atoms for every 3 oxygen atoms 8. B 2 O 3 boron oxide B 2 O 3

9. Magnesium (Mg +2 ) + Oxygen (O -2 ) 1 magnesium atom for every 1 oxygen atom 9. MgO magnesium oxide MgO Mg +2 O -2

10. Aluminum (Al +3 ) + Fluorine (F -1 ) 1 aluminum atom for every 3 fluoride atoms 10. AlF 3 aluminum fluoride AlF 3 F -1 Al +3

11. Potassium (K +1 ) + Iodine (I -1 ) 1 potassium atom for every 1 iodine atom 11. KI potassium iodide KI K +1 I -1

12. Sodium (Na +1 ) + Nitrogen (N -3 ) 3 sodium atoms for every 1 nitrogen atom 12. Na 3 N sodium nitride Na 3 N Na +1 N -3 Na +1

13. Potassium (K +1 ) + Bromine (Br -1 ) 1 potassium atom for every 1 bromine atom 13. KBr potassium bromide KBr K +1 Br -1

14. Lithium (Li +1 ) + Fluorine (F -1 ) 1 lithium atom for every 1 fluorine atom 14. LiF lithium fluoride LiF Li +1 F -1

15. Magnesium (Mg +2 ) + Nitrogen (N -3 ) 3 magnesium atoms for every 2 nitrogen atoms 15. Mg 3 N 2 magnesium nitride Mg 3 N 2 Mg +2 N -3 Mg +2

Questions?

B +3 Cl -1 B Cl 1 3 Boron (B +3 ) + Chlorine (Cl -1 ) boron chloride You can also determine the formula for a compound using the criss-cross method. Take the numbers from the ions superscripts and cross them to become the subscripts in the compound. Look at question #1. 13 BCl 3

Mg +2 N Mg N 3 2 Magnesium (Mg 2+ ) + Nitrogen (N -3 ) Magnesium nitride Look at #15 to practice the criss-cross method again. Mg 3 N 2

K +1 (SO 4 ) K (SO 4 ) Potassium (K +1 ) + Sulfate (SO 4 -2 ) potassium sulfate This also works for polyatomic ions. K 2 SO 4 Parentheses are not used unless a subscript is needed after the polyatomic ion, as you will see in the next example.

Al +3 (SO 4 ) Al (SO 4 ) Aluminum (Al +3 ) + Sulfate (SO 4 -2 ) aluminum sulfate Use parentheses to indicate that more than one of the same polyatomic ion is included in the compound. Al 2 (SO 4 ) 3

If the superscript charges add to zero, DO NOT criss-cross. All compounds have a zero charge, so it takes one of each ion to make the compound: Ca +2 + O -2 CaO B +3 + N -3 BN (+2 and -2 = 0) (+3 and -3 = 0)

Released TAKS Question calcium (Ca +2 ) + chlorine (Cl -1 ) calcium chloride The chemical formula for calcium chloride is --- A) Ca 2 Cl B) CaCl C) CaCl 2 D) Ca 2 Cl 3 Ca +2 Cl -1 Ca Cl CaCl 2

Released TAKS Question According to this information, what is the chemical formula for aluminum sulfate? A) AlSO 4 B) Al 2 (SO 4 ) 3 C) Al 3 (SO 4 ) 2 D) Al 6 SO 4 Al 3+ SO 4 2- Al +3 (SO 4 ) Al (SO 4 ) Al 2 (SO 4 ) 3

Questions? Good job!!! Dont forget to put your name on your paper before you turn it in.

K +1 B +3 Ca +2 Li +1 Mg +2 Na +1 K +1 Ca +2 Na +1 Cl -1 F -1 Br -1 O -2 S -2 Mg +2 Al +3 Na +1 K +1 Al +3 B +3 I -1 Br -1 Mg +2 N -3 P -3 S -2 Cl -1

1.Boron (B +3 ) + Chlorine (Cl -1 ) boron chloride ____________ 2.Magnesium (Mg +2 ) + Chlorine (Cl -1 ) magnesium chloride ____________ 3.Sodium (Na +1 ) + Chlorine (Cl -1 ) sodium chloride ____________ 4.Calcium (Ca +2 ) + Sulfur (S -2 ) calcium sulfide ____________ 5.Aluminum (Al +3 ) + Nitrogen (N -3 ) aluminum nitride ____________ 6.Calcium (Ca +2 ) + Bromine (Br -1 ) calcium bromide ____________ 7.Potassium (K +1 ) + Chlorine (Cl -1 ) potassium chloride ____________ 8.Boron (B +3 ) + Oxygen (O -2 ) boron oxide ____________ 9.Magnesium (Mg +2 ) + Oxygen (O -2 ) magnesium oxide ____________ 10.Aluminum (Al +3 ) + Fluorine (F -1 ) aluminum fluoride ____________ 11.Potassium (K +1 ) + Iodine (I -1 ) potassium iodide ____________ 12.Sodium (Na +1 ) + Nitrogen (N -3 ) sodium nitride ____________ 13.Potassium (K +1 ) + Bromine (Br -1 ) potassium bromide ____________ 14.Lithium (Li +1 ) + Fluorine (F -1 ) lithium fluoride ____________ 15.Magnesium (Mg +2 ) + Nitrogen (N -3 ) magnesium nitride ____________ Write the chemical formula for the following compounds. Place the cutouts in the corresponding boxes on the following pages.

1. B +3 + Cl Mg +2 + Cl Na +1 + Cl Ca +2 + S -2

5. Al +3 + N Ca +2 + Br K +1 + Cl B +3 + O -2

9. Mg +2 + O Al +3 + F K +1 + I Na +1 + N -3

13. K +1 + Br Li +1 + F Mg +2 + N -3

1.Boron (B +3 ) + Chlorine (Cl -1 ) boron chloride _____BCl 3 _____ 2.Magnesium (Mg +2 ) + Chlorine (Cl -1 ) magnesium chloride ____ MgCl 2 _____ 3.Sodium (Na +1 ) + Chlorine (Cl -1 ) sodium chloride _____NaCl _____ 4.Calcium (Ca +2 ) + Sulfur (S -2 ) calcium sulfide _____CaS _____ 5.Aluminum (Al +3 ) + Nitrogen (N -3 ) aluminum nitride _____AlN ______ 6.Calcium (Ca +2 ) + Bromine (Br -1 ) calcium bromide ____CaBr 2 ______ 7.Potassium (K +1 ) + Chlorine (Cl -1 ) potassium chloride _____KCl _______ 8.Boron (B +3 ) + Oxygen (O -2 ) boron oxide ____ B 2 O 3 _______ 9.Magnesium (Mg +2 ) + Oxygen (O -2 ) magnesium oxide _____MgO ______ 10.Aluminum (Al +3 ) + Fluorine (F -1 ) aluminum fluoride _____AlF 3 ______ 11.Potassium (K +1 ) + Iodine (I -1 ) potassium iodide _____ KI_______ 12.Sodium (Na +1 ) + Nitrogen (N -3 ) sodium nitride ____Na 3 N ______ 13.Potassium (K +1 ) + Bromine (Br -1 ) potassium bromide _____KBr _______ 14.Lithium (Li +1 ) + Fluorine (F -1 ) lithium fluoride _____ LiF ________ 15.Magnesium (Mg +2 ) + Nitrogen (N -3 ) magnesium nitride ____Mg 3 N 2 ______ Key

Notes to Teacher If you want to have the students cut out the ions themselves, they will need two copies of the ion sheet to complete the assignment. In order to save time you may want to try having the students cut out the ions as homework. If you are a paper-saving type, you can make class sets of ions (just one sheet per student since they can reuse ions) and not have the students actually paste them on the answer sheets. Instead, you can: –Have a class set of ions premade and laminated. Put them in ziploc bags to keep them separate. You can also laminate a class set of answer sheets if you want the students to have a reusable place to work out their solutions. –Print the ion pages on magnetic paper and cover it with adhesive laminate prior to cutting out the pieces. Then place these sets in ziploc bags. Students can rearrange the ions on whiteboards or cheap cookie tins (which can be purchased at most dollar stores) before writing down their answers.