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

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

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 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

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 O 2 8CO H 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 H 2 O 3CH 4 + 4Al(OH) 3 Balance these skeleton equations:

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 ½

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

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)

Nuclear equations Q. Write the beta decay for C-14 In all cases, charge and mass must be balanced Practice: pg , Q6, Q3 C 14 6 e 0 N Po He 4 2 Pb Q. Write the alpha decay for 209 Po Q. Complete this fission reaction Kr U n 1 0 Ba n

6. a) b) c) d) e) Ra He 4 2 Rn Sr P Re He 4 2 Tc a) b) c) d) e) Br e 0 Kr Pu He 4 2 U N 14 7 C p He 4 2 O 18 8 F n e 0

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:

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