Miderm Sheet

← Muon
← Is created when a neutrino collides and combines with an H2O proton (weak force)

← Creates blue light

← High energy; travels faster than the speed of light (in water)

← Neutrino
← Type of particle: Lepton (like electrons and muons)

← Most abundant particle in the universe

▪ 1016 neutrinos are passing through your body at any point in time

← Theoretically discovered by Wolfgang Pauli (1930); actually discovered in 1955

← Produced during nuclear reaction or changes

← At least 6 different “kinds” (3 matter; 3 anti-matter)

← Very weakly interact with matter

← Modern Atomic Theory (John Dalton, 1800)
← Cells: “individual building blocks of matter”

← Cells: “smallest unit of an element which best represents the physical and chemical properties of that element”

← Element: “matter in which the fundamental building blocks are atoms”

▪ “Carefully” arranged on Periodic Table, represented by symbols (eg 11Na)

← Chemistry: “the science of the composition and structure of materials, their properties, and their chemical changes”

← Elements
← 4 classes: Nobles Gases, Metals, Metalloids, Nonmetals

← Alkali Metals (IA)

← Alkaline Earth Metals (IIA)

← Transition Metals (B)

← Halogens (VIIA)

← Electron
← Discovered by J. J. Thomson 1897 (also discovered charge to mass ratio (1.76*10^8 C/g))

▪ Cathode ray (with high voltage source) through Anode and magnetic field onto fluorescent screen, gave off alpha rays and X-rays (discovered by W. Röentgen (1896) by “accident”)

← A fundamental particle (lepton)

← Fermion: it has a spin (±½)

← Give off β when decays

← Milliken’s oil drop experiment helped figure out charge(1.6*10^-19) and mass(9.09*10^-28 g) of electron

← Atomic Structure Models
← J. J. Thomson Model (1905)

← Rutherford Model (1911)

▪ Positive charge in nucleus, negative charge away

▪ Proved positive nucleus through Gold Foil experiment

▪ 24He++ = α

▪ e- = -10e = β-

▪ e+ = +10e = β+ ( Antimatter

← Bohr Model (1913)

▪ Electrons orbit nucleus in limited number of orbitals

← Atomic Number ~ 82208Pb

← Identifies the element and is either the number of protons in the nucleus of the atom or the total number of electrons surrounding the nucleus

← Mass Number/Atomic Mass~ 82208Pb

← The sum of all the neutrons and protons in the nucleus of the atom:mass of specific isotope

← Atomic Weight ~ K1939.10

← Average mass of all the isotopes of that element , measured with atomic mass units (amu)

← Isotopes: atoms having same number of protons9 but a different number mass number because of a different number of electrons

← Atoms

▪ Electrons = almost 0 amu

▪ Protons = 1 amu

▪ Neutrons = 1 amu

▪ Quarks (↑↓) and Gluons

← Periodic property

▪ Atomic radius

• Decreases to the right

• Increases down

← Amu = 1/12 * 612C atom

▪ # (atoms or Molecules) * # amu/(atom or molecule)*1g/6.022x1023 amus = mass in grams

← Mole: the quantity of something that contains 6.022x1023 (NA) units of that something

← Electronegativity (Ē)

← “the relative tendency of an atom forming a chemical bond to pull electrons toward itself” 0-4

← Fr has lowest (.7), F has highest (3.98).

← Higher ^> on table

← Metals have relatively low electronegativity

▪ Metal atoms tend to lose electrons by a process called oxidation

▪ Any substance that undergoes oxidation is called a reducing agent

▪ Some metals have multiple Oxidation Numbers

• Cu ( Cu+1 or Cu+2

• Fe ( Fe +2 or Fe +3

← Nonmetals have relatively high electronegativity

▪ Nonmetallic elements tend to gain electrons (process called Reduction)

• Reduction: 4Fe + 3O2 ( 2Fe2+3O3-2

← Valence Electrons

← Cation: small, positive ions

← Anion: large, negative ions

← Lewis Dot Structure:

← Chemical Bonds

← “an [electrical] force of attraction between separate atoms, ions, or molecules”

← 3 strong classes of chemical bonds

← Primary Bonds

▪ Covalent bonds (nonmetal + nonmetal)

• Forms molecules

▪ Ionic bonds (metal + nonmetal)

• Not a molecule

• Solids under standard conditions

• “high” melting point

• excellent electrical Insulations (as solids)

• hard, brittle

• only Na+ salts are widely soluble in water

• Generally crystalline structure (organized) (not amorphous)

▪ Metallic bonds (between the individual atoms in a metal)

• Highly crystalline structure: Electron “sea” highly organized and static

← Crystals

← Properties:

▪ High melting point

▪ Low electrical conductivity in the solid state (very good insulator)

▪ Group IA “salts” are very soluble in H2O (H2O solutions are very good electrical conductors)

← Examples: Ag2+1O-2, Be+2O-2

← X-ray diffraction helps show Crystal structure

← Kidney stone: ionic crystalline structure of calcium deposits

← Transmutation

← Changing one element into another element

← RHIC: Relativistic Heavy Ion Collider (in US)

← PET (Positron Emission Tomography): injects unstable nuclei in blood that decay into positrons. When positrons are emitted, they are annihilated by electrons because they are antimatter. That lets off radiation, which is studied.

←

← Nuclear Reactions

← Bombardment

▪ 4020Ca + 115B ( AZX + 42He A=47; Z=23; X=V; AZX=4723V

▪ 94Be + 42He ( 126C + 10n discovery of neutrons

▪ 10n ( 11p + 0-1e (free neutron is unstable and decays into proton and electron)

▪ 11p ( 10n + 0+1e (Proton becomes neutron and positron (antimatter))

← α (42He) emission:

▪ 20882Pb ( AZX + 42He AZX=20420Hg

← β-1 (0-1e) emission (neutron becomes proton)

▪ 3416S ( AZX + 0-1e AZX=3417Cl

← β+1 (0+1e) emission (Proton becomes netron)

▪ 2312Mg ( AZX + 0+1e AZX=2311Na

← Carbon-14 dating

▪ 147N + 10n ( 146C + 11H

▪ 146C ( 147N + 0-1e

▪ t1/2 = 5.73 x 103 years

← Uranium-238 Dating

▪ 23892U ( 20692Pb + 843α + 6 0-1β

▪ t1/2 = 4.51 x 109 years

← Breeder Reactor

← Nuclear Fission type reactor that would have unlimited amounts of energy possible

← Produces more fuel than it consumes

← Moral issue: Produces 23994Pu, which can be used for atom bombs

← 23892U + 10n ( 23992U

← 23992U ( 23993Np + 0-1β

▪ t1/2 = 23.4 minutes

← 23993Np (23994Pu + 0-1β

▪ t1/2 = 2.35 days

← Electrochemistry

← Oxidation: loss of electrons

← Reduction: gain of electrons

← Anode: negative terminal, oxidation takes place here

← Cathode: positive terminal, reduction takes place here

← Simplified way to represent the Zn/Cu cell:

▪ Zn(s) | Zn++(aq)(1M) || Cu++(aq)(1M) | Cu(s)

▪ Anode salt bridge cathode

▪ E0cell = E0cathode – E0anode = .34V – (-.76V) = 1.10V

▪ Zn (anode) and C (graphite) (cathode)

▪ Alkaline batteries (most) cost more but are more stable

▪ 2 3 volts in series = 6 volts and 1 cell life

▪ 2 3 volts in parallel = 3 volts and 2 cell life

← Standard Reduction Potentials/ Electrolysis

← Voltaic (Galvanic) (Source) Cell:

▪ spontaneously generates electrical energy to do useful work

← Electrolytic (Load) Cell: (opposite)

▪ Involves a nonspontaneous electrolysis process during which an outside power source forces a reaction to take place

▪ 2H2O(l) ( 2H2(g) + O2(g) nonspontaneous

← Electrolysis of water:

▪ Beaker of water with Sulfuric Acid (H2SO4) to make it slightly acidic

▪ 2 Pt electrodes in water with a power source to pull electrons away from one of the electrodes

▪ Anode (oxidation)

• 2H2O(l) ( O2(g) + 4H+(aq) + 4e-

▪ Cathode (reduction)

• (2H+(aq) + 2e-- ( H2(g)) *2

▪ End up with:

• 2H2O(l) ( 2H2(g) + O2(g)

← Electroplating one metal onto another metal is an example of electrolysis.

▪ The metal always plates out at the cathode, which is a reduction reaction

▪ Ag+(aq) + e- ( Ag(s)

▪ Electroplating (on cathode because it gains mass) is a nonspontaneous process that must be forced to occur by applying electrical energy from an outside source

▪ Concentration (M) of substance in H2O stays the same after reaction (but mass of electrode decreases)

▪ Pb/H2SO4 cell (when discharging):

• Terminals: + (PbO2) and – (Pb)

• Sulfuric acid (H2SO4) inside

• Anode: Pb(s) + SO4-2(aq) ( PbSO4(s) + 2e-

• Cathode: PbO2(s) + 2e- + SO4-2(aq) + 4H+(aq) ( PbSO4(s) + 2H20

• Net: Pb(s) + PbO2(s) + 4H+(aq) + 2SO4-2(aq) ( 2PbSO4(s) + 2H20

▪ Lithium Ion Cells (when discharging)

• E0cell = 3.7V (perhaps the highest of all practical cells)

• Anode: porous graphite; has (saturated with Li+ (process is called intercalation))

• Li+ goes to cathode (not oxidation, no electrons lost) and is intercalated there

• Organic material used instead of water

• CLi ( Li+ + C- (leaves negative charge on graphite, pushing electrons away)

• Li+ + Li1-xCoO2 ( Li1-x+yCoO2

▪ Lithium Ion Cells (when recharging)

• Force electrons to go in opposite direction (to cathode)

← Oxidation-Reduction Reaction (because Oxidation numbers are changing)

▪ Zn0(s) + 2H+1Cl-1(aq) ( Zn+2Cl2-1(aq) + H20

▪ Anode (oxidation): Zn(s) ( Zn+2 (aq) + 2e-

▪ Cathode (reduction):2H+1 (aq) + 2e- ( H2 (g)

← Corrosion

← An electrochemical process involving oxidation

← Fe0(s) + [H2O + O2] ( Fe+2 ( Fe+3 + 1e-

▪ Anode: 2x(Fe(s) ( Fe+2(aq) + 2e-)

▪ Cathode: O2(g) + 4H+(aq) + 4e- ( 2H2O(l)

▪ Net: 2Fe(s) + O2(g) + 4H+(aq) ( 2Fe+2(aq) + 2H2O(l)

▪ E0 = 1.67V

▪ Rust: Fe2O3 x H2O (with water if hydrated rust)

▪ Salts (NaCl, CaCl2) speed up the process

← Corrosion

← Oxidation of Al

▪ Al2O3 is an excellent, tough barrier (eg covers on Al pipes) to prevent corrosion (anodizing)

← Oxidation of Cu

▪ CuCO3 (green coating) also gives protection to the underlying Cu (eg on Statue of Liberty)

← Oxidation of Ag

▪ Ag2S (black, tarnish) gives some protection to the underlying Ag

← Galvanizing

▪ Anode: Zn (Zn+2 + 2e-

▪ Cathode: Fe+2 + 2e- ( Fe

▪ Cathodic protection

• Mg is better at protecting from corrosion than Zn

← An Fe surface may be protected by covering it with organic cratings or with some other metal. A Sn can is a can with a thiin layer of Sn over Fe. But watch out!

▪ Should the Sn surface be scratched, the Fe will become the anode and Sn the cathode, and it will speed up the corrosion.

← Fuel cell vehicles

← PEM Fuel Cell (attempted by GM)

▪ Hydrogen is supplied to the fuel cells; so is air, by the compressor;

▪ oxygen (air) + hydrogen = electricity (sent to the traction inverter module, TIM)

▪ Only byproduct: water vapor/moisture

▪ Porous C anode/cathode; Pt catalyst;

← Fuel Cell Characteristics:

▪ Potentially highly efficient producer of electrical energy

▪ A continuous supply of fuel (eg H2) and oxidizing agent (eg O2)

▪ Low cell voltage (E0 = .7V)

▪ Many cells connected in series (a stack is necessary to power high-powered vehicles)

▪ Few moving parts

▪ Potentially low “exhaust” pollution (eg H2O)

▪ Technical fuel storage problems (eg 104 psi for H2)

▪ Problems with H2 production and distribution

▪ Reformers for automobiles are not sufficiently developed

← How a fuel cell works:

▪ Anode: 2x(H2(g) ( 2H+(aq) + 2e-) (H2O and catalyst needed)

▪ Cathode: O2(g) + 4e-- ( 2O-2(aq) “

▪ Net: 2H2(g) + O2(g) ( 2H2O(l) + waste heat