1. Oxidation – Reduction

2. Redox reactions
Also known as electron transfer reactions

3. One substance gets oxidized
Redox reactions
One substance gets oxidized
loses electrons
- Known as the REDUCING agent
One substance gets reduced
Gains electrons
Known as the oxidizing agent

4. Ex:
4 Fe (s) + 3 O2 → 2 Fe2O3 (s) when the iron reacts with the oxygen, it transfers 3 electrons to oxygen – iron is oxidized, oxygen is reduced

5. LEO says GER
Redox reactions

6. Ex: A piece of copper is immersed in a solution of copper(II) sulfate
Fe(s) + CuSO4(aq)  Cu FeSO4
Just looking at the metals (they are the only ones change oxidation state…..
Redox reactions

7. Rules for determining oxidation numbers
1. For an atom in it’s elemental form the oxidation number is 0
ex: Mg, Fe, Cu, H2, O2
Redox reactions

8. Redox reactions
Rules for determining oxidation numbers
2. For a monatomic ion, it’s oxidation number is equal to its charge
ex: Mg 2+ oxidation number = +2
Cl oxidation number = -1

9. Rules for determining oxidation numbers
3. The oxidation number for oxygen in a MOLECULAR compound is -2
ex: H2O, CO2
Redox reactions

10. Rules for determining oxidation numbers
4. Hydrogen
+1 when it is bonded to a nonmetal
ex: HCl
-1 when it is bonded to a metal
ex: MgH2

11. Rules for determining oxidation numbers
5. For other covalent compounds not containing oxygen or hydrogen, the most electronegative element has an oxidation number equal to its charge as an ion
ex: BF3 ; the oxidation number for fluorine is -1

12. Rules for determining oxidation numbers
6. The sum of all the oxidation numbers for all of the atoms in a compound must equal the overall charge of the compound
ex: H2O
oxidation number of H = +1(2) = +2
oxidation number of O = -2
Sum of oxidation numbers = 0

13. 7. For a polyatomic ion, the sum of the oxidation numbers for each of the atoms in the compound is equal to the ionic charge on the polyatomic ion.

14. Ex: ClO3-
oxidation number of O = -2(3) = +6
oxidation number of Cl must be +5 so that the overall charge = -1

15. Sample problems
Calculate the oxidation number for sulfur in each of the following ions:
Sulfide ion, S-2
sulfite ion, SO3-2
sulfate ion, SO4-2
Thiosulfate ion, S2O3-2

16. Sample problems
Sulfide ion, S-2
Oxidation number would be -2 because
For a monatomic ion, it’s oxidation number is equal to its charge

17. Sample problems
sulfite ion, SO3-2
Oxidation number would be +4 because
Oxygen is assigned a -2 charge x 3 = -6
So then S has to be +4 so that the overall charge is -2

18. Sample problems
sulfite ion, SO4-2
Oxidation number would be +4 because
Oxygen is assigned a -2 charge x 3 = -6
So then S has to be +6 so that the overall charge is -2

19. Sample problems
sulfite ion, S2O3-2
Oxidation number would be +2 x 2 = +4 because
Oxygen is assigned a -2 charge x 3 = -6
So then S has to be +6 so that the overall charge is -2

20. Calcium metal gets oxidized (loses electrons)
Redox reactions
How can you tell what gets oxidized and what gets reduced?
2Ca(s) O2(g)  2CaO(s)
Calcium metal gets oxidized (loses electrons)
Oxygen gas gets reduced (gains electrons)

21. Oxidizing and reducing agents
Oxidizing agent is a substance that accepts the electrons
Reducing agent is a substance that transfers the electrons

22. Oxidizing and reducing agents
Fe(s) + S(s) → FeS(s) Fe = 0 Fe = +2 S = 0 S = -2 Iron is oxidized and sulfur is reduced So iron is the reducing agent and sulfur is the oxidizing agent

23. Molecular equation – represents the complete formulas of all the reactants and products
K2CrO4 (aq) + Ba(NO3)2  BaCrO4 + KNO3
Complete ionic equation- includes all ions
K+(aq) + CrO4 2-(aq)+ Ba2+(aq) + NO31-(aq)+ K+(aq) 
BaCrO4 K+(aq)+ NO31-(aq)
K+ and NO31- are called spectator ions- they do not participate in the reaction

24. Nuclear Chemistry

25. Chemical vs. Nuclear Reactions
Chemical Reactions-
A rearrangement of atoms and molecules by breaking and forming bonds
-involves electrons
Nuclear Reactions-
Combining, splitting or decay the nuclei of atoms.

26. Nuclear Chemistry involves the NUCLEUS of the atom.
That means…. the protons and neutrons will undergo a change (nuclear reactions)
Nuclear reactions usually involve radioactive elements

27. Radioactive Elements are NOT stable….
…because of the proton to neutron ratio.

28. Radioactive elements will give off particles and energy until they become stable (non-radioactive)

29. Radioactive elements change by themselves
Of the 119+ different atoms….
…there are more than 1500 different nuclei, only 264 are stable

30. Discovery of Radioactivity
Professor Roentgen – found that certain elements gave off X-rays but didn’t know what caused them.

31. Two Kinds of Nuclear Reactions
1. Fission-
Splitting the nucleus
2. Fusion-
Combining nuclei

32. Transuranium Elements
The elements past uranium (#92)
All radioactive

33. Showing Radioactive Atoms.
Use Isotope Notation
C-12
C-14
Mass number 12 14 C C 6 6
Atomic number

34. Types of Radiation
Alpha Particle: α
Beta Particle: β
Gamma Ray: γ

35. Alpha Decay -when an atom gives off an alpha particle (helium nucleus)
Alpha Particle = 2p and 2n
-atomic # goes down 2 and atomic mass goes down 4

37. Written as: 4
He (in nuclear equations) 2 or
a (in decay series)

38. -U-238 turns into Th-234 when it gives off an alpha particle
Ex.
(nuclear equation)
238 4
234 U Th He + 90 92 2

39. Alpha Particles -weakest radiation
-can be stopped by a piece of paper.
-can burn flesh

40. Affects of Alpha Particles on Body
will not penetrate the outer layer of skin
dangerous if inhaled or swallowed.
Cells in lining of the lungs or internal organs will be changed (mutated) or killed
lung cancer cases among uranium miners from inhaled and ingested alpha sources is much higher than those of the public at large.

41. Radon Radon gas produced by the decay of radium-226
emits alpha particles
poses a hazard to lungs and airways when inhaled.

43. e e -1 +1 Beta Decay Two types: Beta minus decay Beta plus decay
- Written as b-
Written as β+ or e e -1 +1

44. A. BETA MINUS DECAY:
Neutron decays into a proton, an electron and an antineutrino
Mass number remains the same but atomic # increases by 1

45. B. BETA PLUS (positron) DECAY
A proton decays into a neutron, a neutrino and a positron
Positron has the mass of an electron but is positively charged
Mass number remains the same
Atomic Number decreases by 1

46. -100x more penetrating than an alpha particle
Beta Particles
-100x more penetrating than an alpha particle
-can be stopped by clothing or wood
-travel at the speed of light
-usually accompanies other modes of radioactive decay

47. Gamma Decay -gives off a gamma ray (γ )
- a release of high energy electromagnetic radiation from nucleus
-it’s pure energy not a particle
-Atomic # and mass stay the same, just changes to an atom with less energy
- needs thick walls of concrete or lead to stop it.

49. Nuclear equations Alpha decay equation
Show one transformation of a decay series
Must be equal on both sides. !!!!!!!!!
Alpha decay equation
237 Np 93

50. Beta minus decay equation32 P 15
Beta plus decay equation (positron decay) 15 O 8