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IB Chemistry on Atomic Structure, Particle Physics and Relative Atomic Mass
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Atomic Structure
Atomic Size radius •Order of magnitude – (10-10 – 10-12)m •Radius Li atom – (1.5 x 10-10)m •Radius nucleus – (1 x 10-14)m
1nm – 1 x 10-9 m 1pm – 1 x 10-12 m 1A - 1 x 10-10 m
Radius Li
atom
Radius Nucleus
Li atom Elementary particles making up nucleon (protons + neutrons)
Nucleon –made up of (protons + neutrons) Protons – made up of 2 up quarks + 1 down quark Neutron – made up of 2 down quarks + 1 up quark
Unit conversion
Structure within atom
Recent discovery particles with help of Large Hadron Collider
Video on new particles physics
http://astronomyonline.org/ViewImage.asp?Cate=Home&SubCate=MP01&SubCate2=&Img=%2FScience%2FImages%2FAtomicStructure.jpg&C
pt
http://justintymewrites.wordpress.com/2012/06/20/the-standard-model-in-laymans-terms2/
Discovery timeline Democritus to Quantum model
Video on timeline discovery
Discovery of elementary particles Elementary particles
Structure within atom
Video on new particles physics
Recent discovery particles from Large Hadron Collider
Higgs boson leftover excitation of particles of Higgs field
Discovery of Higgs boson and Higgs field
Particles interact with Higgs field to produce mass
Video on Higgs field part 1
Video on Higgs field part 2
Higgs Boson Discovery Wins Nobel Prize for Physics
Video on NOBEL PRIZE 2013 !!!!!!
Atomic Structure
Atomic Size radius •Order of magnitude – (10-10 – 10-12)m •Radius Li atom – (1.5 x 10-10)m •Radius nucleus – (1 x 10-14)m
Scale/size of matter from smallest to largest
Excellent Flash on scale of universe Excellent Flash on biological cells Video on scale of universe
1nm – 1 x 10-9 m 1pm – 1 x 10-12 m 1A - 1 x 10-10 m
Radius Li
atom
Radius Nucleus
Li atom Elementary particles making up nucleon (protons + neutrons)
Nucleon –made up of (protons + neutrons) Protons – made up of 2 up quarks + 1 down quark Neutron – made up of 2 down quarks + 1 up quark
Unit conversion
Elementary particles Structure within atom
Recent discovery particles from Large Hadron Collider
Higgs boson leftover excitation of particles of Higgs field
Discovery of Higgs boson and Higgs field
Particles interact with Higgs field to produce mass
Video on Higgs field
Mass (proton + neutron)- due to interaction between up quarks/down quarks with gluons (energy fluatutions)
Proton -2 up quarks
1 down quark
Neutron -1 up quark
2 down quarks
What is Higgs Boson ? What is Higgs Field ?
Excellent videos –Particles interact with Higgs field to create MASS
Video (Ted Talk) Video (Minute physics) Video (RI) Video (Veratasium)
Nuclear reaction vs Chemical reaction
Nuclear reaction • Involve protons/neutrons in nucleus • Decomposition of nucleus into smaller nuclei • Energy released greater • Conservation of charge / atomic mass number
Chemical reaction • Involve outer most electrons • Transfer/sharing/loss of electrons • Energy released less • Conservation of mass and charge
2Na + CI2 2NaCI
http://ths.talawanda.net/~BrambleN/classroom/Chemistry/Notes/Section%206A%20and%206B/RadioactiveDecay.htm
http://www.classhelp.info/Biology/AUnit3Biochemistry.htm
Type radiation
Nature radiation
Symbol Penetration (mass,m/charge,e
)
Ionising power (removing electron)
Alpha Helium nucleus
α Low ratio (high m/e)
High
Beta High energy electron
β Moderate Moderate
Gamma High frequency electromagnetic
radiation
γ High ratio (small m/e)
Low
Type of radiation
Nuclear equation- decay of nucleus Chemical equation – valence electrons
Transfer electrons
Sharing electrons
Nuclear reaction
http://ths.talawanda.net/~BrambleN/classroom/Chemistry/Notes/Section%206A%20and%206B/RadioactiveDecay.htm
http://molaire1.perso.sfr.fr/e_radioactiv.html
Alpha Decay •Losing an alpha particle – helium nucleus •Daughter nuclei lower in proton number •Mass of 4 (2 proton + 2 neutron) •+2 charged (only 2 protons) = +2 •Decay of uranium, thorium, actinium
Beta Decay •Losing beta particle –Electron/positron •Daughter nuclei higher in proton number •Negative charge (-1) •Decay neutron proton + electron
Alpha Decay Beta Decay
Gamma Decay
Gamma decay •Losing a γ particle - electromagnetic radiation of high frequency •Daughter nuclei no change in atomic mass
α β
Unstable nucleus of atom Decay by emitting ionizing particles
+
Difference Between Alpha, Beta and Gamma Radiation
Alpha Decay •Lose alpha particle – helium nucleus •Mass He- 4 (2 proton + 2 neutron) •+2 charged (2 proton + 2 neutron + 0 e) •Daughter nuclei lower in proton number
Beta Decay •Lose beta particle –Electron/beta β •Negative charge (-1) •-1 charged (β or electron) •Daughter nuclei higher in proton number
Gamma decay •Lose a γ particle – electromagnetic radiation of high frequency •Daughter nuclei no change in atomic mass
Nucleus > 84 protons • Unstable, radioactive decay • Decay depends on ratio neutron/proton
Decay depend on ratio neutron/proton Neutron/proton ratio LOW – Proton rich – Decay to reduce proton - Alpha decay, α (proton number )
Mass number always Conserved/Same
Decay depend on ratio neutron/proton Neutron/proton ratio HIGH – Neutron rich – Decay to reduce neutron -Beta decay β ( Neutron Proton + electron) -Ratio decrease
Decay depend on ratio neutron/proton Neutron/proton ratio HIGH /LOW -Gamma decay γ, is associated along with Alpha and Beta
Video on α decay Video on β decay Video on γ decay
Radioactive isotopes Half-life
Uranium 238 4.5 x 109
Carbon-14 5.7 x 103
Radium-226 1.6 x 103
Strontium-90 28 years
Iodine-131 8.1 days
Bismuth-214 19.7 minutes
Polonium-214 1.5 x 10-4
Isotopes
Stable Isotopes Unstable Isotopes
Unstable Isotopes – emits radiation
RADIOISOTOPES
Simulation isotope 12C, 13C, 14C
Radioisotopes •Half-life – time taken for conc/amt isotope to fall to half of its original value. •Half life decay – always constant
Shorter half-life More unstable, decay fast
Long half-life More stable, decay slowly
www.sciencelearn.org.nz
Emit radiation form unstable isotope
Simulation isotope 1H, 2H, 3H
Video on Half life
Simulation half life C-14/uranuim
Half-life
Carbon – 3 Isotopes Radiocarbon/carbon dating
• Half life C-14 = 5730 years • Beta (β/electron ) decay
Conclusion Ratio C14/C12 is constant is organism alive Ratio C14/C12 drop organism die
Uses • Age dead organic material/fossil contain Carbon element • Max age limit is 60,000 years old.
Carbon -12 Carbon -14 Carbon -13
Abundance – 99% (Stable) Abundance – 1% (Stable) Abundance – trace amt (Unstable , radioactive)
How is form? • C-14 produce in stratosphere when….. neutron hit a nitrogen atom to form C-14 •C-14 to N-14 by converting neutron proton (proton stay in nucleus), electron emit as β radiation • emit as β ray.
(proton in nucleus – increase proton number)
emit as β ray. •Ratio C14/C12- constant if alive – TAKE in C14 (C12 constant) •Ratio C14/C12- drop if dead - NOT taking C14. (C12 constant)
How it is form?
Radiocarbon/carbon dating
• Half life C-14 = 5730 years • Beta (β/electron ) decay
Carbon -14
Abundance – trace amt (Unstable , radioactive)
How is form? • C-14 produce in stratosphere when….. neutron hit a nitrogen atom to form C-14 •C-14 to N-14 by converting neutron proton (proton stay in nucleus), electron emit as β radiation • emit as β ray.
(proton in nucleus – increase proton number)
emit as β ray. •Ratio C14/C12- constant if alive – TAKE in C14 (C12 constant) •Ratio C14/C12- drop if dead - NOT taking C14. (C12 constant)
Video on C-14 Carbon Dating Video on C-14 Carbon Dating/Fossil Video on C-14 Half life Carbon Dating
Simulation C-14 (Half life) At 100% (Starting)
Simulation C-14 (Half life) At 50% (Starting)
Video on Radiocarbon dating
Click to view simulation
How Radiocarbon dating works?
Radiocarbon/carbon dating
• Half life C-14 = 5730 years
Carbon -14
Beta (β/electron) decay
Video on C-14 Carbon Dating
Video on Radiocarbon dating
How Radiocarbon dating works?
Uses of radioactive isotopes
Radiotherapy/cancer/tumour Tracers/studying metabolic pathways
Cobalt-60
• Half life Co-60 = 5.27 years • Half life I-131 = 8 days
How Gamma rays works? How Radio tracer works?
Iodine-131
Sterilization – killing bacteria/germ Radiotherapy – kill tumor cells High energy electromagnetic ray
Video on Radio tracer Video on Radiotherapy
Gamma γ + β decay
Carbon dating Age of fossil remains
• Radio tracer • Trace the pathway in body • Beta β (90%) and γ (10%) decay
Gamma γ + β decay
6 protons + 6 neutrons
8 protons
No isotopes are present
Proton number = proton
Mass number = proton + neutron
Z
A
Atomic /Mass number
6 protons
Atomic Weight With isotopes present
8 protons + 8 neutrons
Proton number = proton Z
Mean relative mass (atomic weight) A
Video on weighted average
Relative Atomic Mass, (Ar) of an element:
• Number of times one atom of the element is heavier than one twelfth of the mass of a carbon-12
• Relative atomic mass = Mass of one atom of element 1/12 x mass of one carbon-12
• Relative atomic mass for sulphur = 32 (one sulphur atom is 32 x heavier than 1/12 of mass of one (C12)
http://www.tutorvista.com/content/science/science-i/atoms-molecules/atom.php
Relative Atomic Mass
Carbon-12 as standard 1/12 of C12 = 1 unit
Sulphur – 32x heavier
1/12 x = 1 unit
32 unit
6 protons + 6 neutrons
16 protons + 16 neutrons
Relative Atomic Mass is used : • Impossible to weigh an atom in grams • Compare how heavy one atom is to carbon (standard) • One sulphur atom 32x heavier than 1/12 carbon -12 • Carbon -12 used as standard
12
6
32
16
No isotopes are present
Mass number = proton + neutron
Proton number = proton Z
A
Assuming No isotopes present!
Mass number ≠ Average atomic mass (atomic mass unit)
Relative Molecular Mass, (Mr):
• Number of times one molecule is heavier than one twelfth of the mass of a carbon-12
• Relative molecular mass = Mass of one molecule 1/12 x mass of one carbon-12
• Relative molecular mass for H2O= 18 (one H2O is 18 x heavier than 1/12 of mass of one (C12)
http://www.tutorvista.com/content/science/science-i/atoms-molecules/atom.php
Relative Molecular Mass is used : • Impossible to weigh an molecules in grams • Compare one molecule to carbon (standard) • One H2O is 18 x heavier than 1/12 carbon -12 • Carbon -12 is used as standard
Relative Molecular Mass
Carbon-12 as standard 1/12 of C12 = 1 unit
H2O – 18x heavier
1/12 x = 1 unit
16 unit
2 unit
18 unit
+
6 protons + 6 neutrons
8 protons + 8 neutrons
No isotopes are present
Proton number = proton
Mass number = proton + neutron
Z
A
Assuming No isotopes present!
Mass number ≠ Average atomic weight (atomic mass unit)
2 protons
Relative Isotopic Mass
Isotopes – Atoms of same element with • Different number of neutrons • Same number of protons and electrons Due to presence of isotopes, when calculating RAM,
weighted average/mean of all isotopes present is used.
X - No isotopes
RAM/Ar X = 11 • Mass of 1 atom X Mass of 1/12 of 12C • Mass of 1 atom X relative to 1/12 mass of 1 atom 12C Relative Abundance 75% 25%
Mass number = proton + neutron
Proton number = proton Z = 29 protons
A= 29 protons + 35 neutrons = 64
Isotopes Y - TWO isotopes
RAM/Ar Y = 10.5 • Average Mass of 1 atom Y Mass of 1/12 of 12C • Average mass of 1 atom Y relative to 1/12 mass of 1 atom 12C
RAM /Ar, CI = 35.5 • Weighted average mass of 2 isotopes present = (mass 35CI x % Abundance) + (mass 37CI x % Abundance) = (35 x 75/100) + (37 x 25/100) = 35.5
CI - TWO isotopes
Relative Abundance 50% 50%
Z
Presence of isotopes
A
Z
A
11
3
17
35
17
37
3 3
10 11
http://www.tutorvista.com/content/science/science-i/atoms-molecules/atom.php
Relative Atomic Mass Isotopes are present
Weighted average mass- due to presence of isotopes
Relative Isotopic Mass, (Ar) of an element: •Relative isotopic mass = Average mass of one atom of element 1/12 x mass of one carbon-12 • Relative isotopic mass, carbon = 12.01
Video on Isotopes
RAM = 12.01
Relative Abundance 98.9% 1.07%
13
Why RAM is not a whole number?
RAM, C : = (Mass 12C x % Abundance) + (Mass 13C x % Abundance) = (12 x 98.9/100) + (13 x 1.07/100) = 12.01
Video on weighted average Weighted average calculation
Video on Isotopes
RAM calculation
12
Mg - 3 Isotopes
24 Mg – (100/127.2) x 100% - 78.6% 25 Mg – (12.8/127.2) x 100% - 10.0% 26 Mg – (14.4/127.2) x 100% - 11.3%
RAM for Mg : = (Mass 24Mg x % Abundance) + (Mass 25Mg x % Abundance) + (Mass 26Mg x % Abundance) = (24 x 78.6/100) + (25 x 10.0/100) + (26 x 11.3/100) = 24.30
Relative Abundance % Abundance
Pb - 4 Isotopes
204Pb – (0.2/10) x 100% - 2% 206Pb – (2.4/10) x 100% - 24% 207Pb – (2.2/10) x 100% - 22% 208Pb – (5.2/10) x 100% - 52%
RAM for Pb : = (Mass 204Pb x % Abundance) + (Mass 206Pb x % Abundance) + (Mass 207Pb x % Abundance) + (Mass 208Pb x % Abundance) = (204 x 2/100) + (206 x 24/100) + (207 x 22/100) + (208 x 52/100) = 207.20
Convert relative abundance to % abundance
Convert relative abundance to % abundance
Relative Abundance % Abundance
Relative Atomic Mass
Simulation C-14 dating (Half life) Simulation U-238 dating (Half life)
Additional Resources
Video on isotopes using mass spec Video on Particle Physics (Higgs Field)
Simulation on atomic model
Periodic Table from webelement
Simulation isotope 1H, 2H, 3H and 12C, 13C, 14C
Excellent Video on scale of universe
Video on new particles physics
Excellent Video Higgs Field (Ted Talk)
Recommended