3. How molecules are symbolized Cl 2 2Cl 2Cl 2 Molecules may also have brackets to indicate numbers of atoms. E.g. Ca(OH) 2 O H O H Ca Notice that the OH is a group The 2 refers to both H and O How many of each atom are in the following? a) NaOH b) Ca(OH) 2 c) 3Ca(OH) 2 Na = 1, O = 1, H = 1 Ca = 1, O = 2, H = 2 Ca = 3, O = 6, H = 6

4. Balancing equations: MgO The law of conservation of mass states that matter can neither be created or destroyed Thus, atoms are neither created or destroyed, only rearranged in a chemical reaction Thus, the number of a particular atom is the same on both sides of a chemical equation Example: Magnesium + Oxygen (from lab) Mg + O 2 MgO O MgO + MgO However, this is not balanced Left: Mg = 1, O = 2 Right: Mg = 1, O = 1

5. Balance equations by inspection Hints: start with elements that occur in one compound on each side. Treat polyatomic ions that repeat as if they were a single entity. 5 233.5 2746 222 263 C 2 H 6 + O 2 CO 2 + H 2 O a)P 4 + O 2 P 4 O 10 b)Li + H 2 O H 2 + LiOH c)Bi(NO 3 ) 3 + K 2 S Bi 2 S 3 + KNO 3 d)C 2 H 6 + O 2 CO 2 + H 2 O From Mg + O 2 MgO 2Mg + O 2 2MgO is correct Mg + ½O 2 MgO is incorrect Mg 2 + O 2 2MgO is incorrect 4Mg + 2O 2 4MgO is incorrect

6. a)Mg + 2HCl MgCl 2 + H 2 b)3Ca + N 2 Ca 3 N 2 c)NH 4 NO 3 N 2 O + 2H 2 O d)2BiCl 3 + 3H 2 S Bi 2 S 3 + 6HCl e)2C 4 H 10 + 13O 2 8CO 2 + 10H 2 O f)6O 2 + C 6 H 12 O 6 6CO 2 + 6H 2 O g)3NO 2 + H 2 O 2HNO 3 + NO h)Cr 2 (SO 4 ) 3 + 6NaOH 2Cr(OH) 3 + 3Na 2 SO 4 i)Al 4 C 3 + 12H 2 O 3CH 4 + 4Al(OH) 3 Balance these skeleton equations:

7. We have looked at several types of reactions without worrying about balancing However, all equations should be balanced Predict the products and balance these: (recall, metals above replace metals below, reactions with water yield metal hydroxides) Cu + Fe 2 (SO 4 ) 3 NR (no reaction) Zn + Li 2 CO 3 Cu + AlCl 3 K Na Li Ca Mg Al Zn Fe Ni Sn Pb H Cu Hg Ag Au Returning to reaction types Fe + CuSO 4 LiOH + H 2 Al 2 O 3 2 Ni+ NaCl Al+ CuCl 2 Li+ ZnCO 3 Li + H 2 O Al+O 2 33 3223 2 ½222 324

8. Discovery of Radioactivity Radioactivity is the release of energy or particles when an atom disintegrates (demo) Radioactivity was discovered when minerals were exposed to film through an opaque cover The 3 types of radioactivity can be shown by passing emissions through an electrical field: Lead block Radioactive substance Phosphorescent zinc sulfide detection screen + – Strong magnetic or electrostatic field

9. Types of Radioactivity Types of radiation: 1), 2), 3) 1.Alpha ( ) particles are symbolized as 4 2 He 2.Beta ( ) particles (essentially electrons) are 0 –1 e 3.Gamma ( ) rays are symbolized as 0 0 You can determine the composition of each: : mass of 4 u, charge of +2 (2 p +, 2 n 0, 0 e – ) Other symbols: proton = 1 1 p, neutron = 1 0 n There are different terms to describe the different types of nuclear reactions alpha decay means an particle is given off. Other: beta decay, fusion (meaning to bring together), fission (meaning to break apart)

10. Nuclear equations Q. Write the beta decay for C-14 In all cases, charge and mass must be balanced Practice: pg. 222-3, Q6, Q3 C 14 6 e 0 N 14 7 + Po 209 84 He 4 2 Pb 205 82 + Q. Write the alpha decay for 209 Po Q. Complete this fission reaction Kr 94 36 U 235 92 n 1 0 Ba 139 56 + n 1 0 + 3 +

11. 6. a) b) c) d) e) Ra 226 88 He 4 2 Rn 222 86 +Sr 99 38 P 32 15 Re 187 75 He 4 2 Tc 99 43 3.a) b) c) d) e) Br 84 35 e 0 Kr 84 36 + Pu 242 94 He 4 2 U 238 92 + N 14 7 C 11 6 + p 1 1 + He 4 2 O 18 8 F 19 9 + n 1 0 + e 0

12. a)2KNO 3 2KNO 2 + O 2 b)2Pb(NO 3 ) 2 2PbO + 4NO 2 + O 2 c)P 4 + 6I 2 4PI 3 d)3MgO + 2H 3 PO 4 Mg 3 (PO 4 ) 2 + 3H 2 O e)Br 2 + 2KI I 2 + 2KBr f)Ca(OH) 2 + 2HNO 3 Ca(NO 3 ) 2 + 2H 2 O g) Bi 2 O 3 + 3H 2 2Bi + 3H 2 O h)3Fe + 2O 2 Fe 3 O 4 i)2CaO + 5C 2CaC 2 + CO 2 Here are some more to balance:

13. Question 3 pg. 252 a)2Li + 2H 2 O H 2 + 2LiOH b)P 4 + 5O 2 P 4 O 10 c)2C 2 H 6 + 7O 2 4CO 2 + 6H 2 O d)CS 2 + 3O 2 CO 2 + 2SO 2 e)2AsCl 3 + 3H 2 S As 2 S 3 + 6HCl f)3AgNO 3 + FeCl 3 3AgCl + Fe(NO 3 ) 3 g)2KClO 3 2KCl + 3O 2 h)2SO 2 + O 2 2SO 3 For more lessons, visit www.chalkbored.com www.chalkbored.com