Oxidation States and Redox: Oxidation and Reduction CT04D01 Science 10 Chemistry

Halogens Alkali Metals Metaloids Non-metals Alkaline Earths   He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Alkaline Earths Weak/Poor Metals Transition Metals Lanthanides Noble Gases Actinides

Ionic Charges All elements want to become like the noble gases! Alkali Metals – lose 1 e Alkaline Earths – Lose 2 e IIIA – Lose 3 e IVA (carbon) – Lose 4 e / Gain 4 e VA (Nitrogen) – Gain 3 e VIA (oxygen) – Gain 2 e Halogen – Gain 1 e Noble Gases - neutral Ionic Charges H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Se Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Rf Db Sg Bh Hs Mt Ds   Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr

(BrINClHOF) Br2, O2, H2, Ne, Zn, Mg, Ca, etc Oxidation Numbers Oxidation numbers always refer to single atoms The oxidation number of an uncombined element is always 0 (this includes diatomics) (BrINClHOF) Br2, O2, H2, Ne, Zn, Mg, Ca, etc The oxidation number of Hydrogen is usually +1 HCl, H2SO4 The oxidation number of Oxygen is usually -2 H2O, NO2, et Oxidation numbers of monatomic ions follow the charge of the ion O2-, Zn2+ The sum of oxidation numbers is zero for a neutral compound LiMnO4 The sum of the oxdiation numbers is the charge of the polyatomic ion SO42-, NO3-, PO33- Only when in completely ionic binary compounds will Alkali Metals (+1), Alkaline Earths (+2), Halogens (-1) NaCl, MgBr2, KF, etc

Polyatomic Ions The polyatomic ions will be given to you but you should be very familiar with them by now!! Let’s determine oxidation numbers for each…. +1 -1 -2 -3 Ammonium NH4+ Chlorate ClO3- Sulfate SO42- Phosphate PO43- Chlorite ClO2- Sulfite SO32- Phosphite Nitrate NO3- Carbonate CO32- Nitrite NO2- Hydroxide OH-

Practice Assigning Oxidation Numbers NO2 N2O5 HClO3 HNO3 Ca(NO3)2 K2CO3

Practice Assigning Oxidation Numbers NO2 N= +4, O = -2 N2O5 N = +5, O = -2 HClO3 H=+1, Cl=+5, O = -2 HNO3 H=+1, N = +5, O = -2 Ca(NO3)2 Ca=+2, N =+5, O= -2 K2CO3 K=+1, C=+4, O= -2 Hint: If it includes a polyatomic ion, you know the overall charge, and oxygen will always be -2, find the other oxidation states next

Practice Assigning Oxidation Numbers Fe(OH)3 K3PO3 CO32- (NH4)Cl Fe(ClO2)2

Practice Assigning Oxidation Numbers Fe(OH)3 Fe =+3, O=-2, H=+1 K3PO3 K=+1, P=+3, O=-2 CO32- C=+4, O =-2 (NH4)Cl N=3-, H=1+, Cl=-1 Fe(ClO2)2 Fe=+2, Cl=3+, O=-2

Redox Equations NOTE: If you get there! Brakke students will need to identify which element is oxidized and which is reduced for a 7

Oxidation-Reduction Reactions All redox reactions have at least one element oxidized and at least one element reduced Occasionally the same element may undergo both oxidation and reduction. This is known as an auto-oxidation reduction We will NOT see this until IB CHEM

Pneumonic Devices…. There are two phrases to help you remember the general practice of oxidation and reduction exchanges LEO says GER OIL RIG

GER! LEO says….. LEO: Loss of Electrons = Oxidation GER: Gain of Electrons = Reduction

OIL: Oxidation is Loss…. RIG: Reduction is Gain…. ….of electrons

Oxidation Numbers Oxidation is the loss of electrons; Reduction is the gain of electrons Oxidation and reduction go together. Whenever a substance loses electrons another substance gains electrons Oxidation Numbers are a system that we can use to keep track of electron transfers with a reaction

Using Oxidation Numbers Careful examination of the oxidation numbers of atoms in an equation allows us to determine what is oxidized and what is reduced in an oxidation-reduction reaction

Using Oxidation Numbers An increase in the oxidation number indicates that an atom has lost electrons and therefore oxidized. A decrease in the oxidation number indicates that an atom has gained electrons and therefore reduced Example 0 +2 +6 -2 +2 +6 -2 0 Zn + CuSO4  ZnSO4 + Cu Zn: 0  + 2  Oxidized Cu: +2  0  Reduced

Exercise For each of the following reactions find the element oxidized and the element reduced Cl2 + KBr  KCl + Br2   Cu + HNO3  Cu(NO3)2 + NO2 + H2O HNO3 + I2  HIO3 + NO2 Look on the following slides for answers……

Exercise 1 For each of the following reactions find the element oxidized and the element reduced 0 +1 -1 +1 -1 0 Cl2 + KBr  KCl + Br2 Br increases from –1 to 0  Oxidized Cl decreases from 0 to –1  Reduced K remains unchanged at +1

Exercise 2 For each of the following reactions find the element oxidized and the element reduced 0 +1 +5 -2 +2 +5 -2 +4 –2 +1 -2 Cu + HNO3  Cu(NO3)2 + NO2 + H2O Cu increases from 0 to +2  Oxidized Some N in nitric acid from +5 to +4  Reduced The nitrogen that ends up in copper nitrate remains unchanged, same for hydrogen and oxygen

Exercise 3 For each of the following reactions find the element oxidized and the element reduced 1 +5 -2 0 +1 +5 -2 +4 -2 HNO3 + I2  HIO3 + NO2 N is reduced from +5 to +4  Reduced I is increased from 0 to +5  Oxidized The hydrogen and oxygen remain unchanged.