IB Chemistry on Atomic Structure, Particle Physics and Relative Atomic Mass

1. Atomic Structure
Unit conversion
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
Radius Li
atom
Radius Nucleus
Li atom
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
1nm – 1 x 10-9 m
1pm – 1 x 10-12 m
1A - 1 x 10-10 m
Elementary particles making up
nucleon (protons + neutrons)
Recent discovery particles with help of Large Hadron Collider
Structure within atom
Video on new particles physics
http://astronomyonline.org/ViewImage.asp?Cate=Home&SubCate=MP01&SubCate2=&Img=%2FScience%2FImages%2FAtomicStructure.jpg&C
pt

2. Discovery timeline Democritus to Quantum model
Discovery of elementary particles
Elementary particles
Video on timeline discovery
Structure within atom
Recent discovery particles from
Large Hadron Collider
Discovery of Higgs boson and Higgs field
Particles interact with Higgs field to produce mass
Higgs boson leftover excitation of particles of Higgs field
Video on new particles physics
Higgs Boson Discovery Wins Nobel Prize for Physics
Video on Higgs field part 1
Video on Higgs field part 2
Video on NOBEL PRIZE 2013 !!!!!!

3. Atomic Structure
Unit conversion
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
Radius Li
atom
Radius Nucleus
Li atom
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
1nm – 1 x 10-9 m
1pm – 1 x 10-12 m
1A - 1 x 10-10 m
Elementary particles making up
nucleon (protons + neutrons)
Scale/size of matter from smallest to largest
Excellent Flash on scale of universe
Excellent Flash on biological cells
Video on scale of universe

4. Elementary particles
Structure within atom
Recent discovery particles from
Large Hadron Collider
Particles interact with Higgs field to produce mass
Discovery of Higgs boson and Higgs field
Mass (proton + neutron)- due to interaction between
up quarks/down quarks with gluons (energy fluatutions)
Proton -2 up quarks
1 down quark
Video on Higgs field
What is Higgs Boson ?
What is Higgs Field ?
Higgs boson leftover excitation
of particles of Higgs field
Neutron -1 up quark
2 down quarks
Video (Veratasium)
Excellent videos –Particles interact with Higgs field to create MASS
Video (RI)
Video (Ted Talk)
Video (Minute physics)

5. Nuclear reaction vs Chemical reaction
Chemical reaction
Nuclear reaction
•
•
•
•
•
•
•
•
Involve protons/neutrons in nucleus
Decomposition of nucleus into smaller nuclei
Energy released greater
Conservation of charge / atomic mass number
Involve outer most electrons
Transfer/sharing/loss of electrons
Energy released less
Conservation of mass and charge
Chemical equation – valence electrons
Nuclear equation- decay of nucleus
2Na + CI2  2NaCI
Transfer electrons
Sharing electrons
Type of radiation
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
http://ths.talawanda.net/~BrambleN/classroom/Chemistry/Notes/Section%206A%20and%206B/RadioactiveDecay.htm
http://www.classhelp.info/Biology/AUnit3Biochemistry.htm

6. Nuclear reaction
Alpha Decay
Unstable nucleus of atom
Decay by emitting ionizing particles
α
β
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
Beta Decay
•Losing beta particle –Electron/positron
•Daughter nuclei higher in proton number
•Negative charge (-1)
•Decay neutron  proton + electron
Gamma Decay
Gamma decay
•Losing a γ particle - electromagnetic radiation of high
frequency
•Daughter nuclei no change in atomic mass
http://ths.talawanda.net/~BrambleN/classroom/Chemistry/Notes/Section%206A%20and%206B/RadioactiveDecay.htm
http://molaire1.perso.sfr.fr/e_radioactiv.html
+

7. Difference Between Alpha, Beta and Gamma Radiation
Nucleus > 84 protons
• Unstable, radioactive decay
• Decay depends on ratio neutron/proton
Mass number always Conserved/Same
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
Decay depend on ratio neutron/proton
Neutron/proton ratio LOW – Proton rich
– Decay to reduce proton
- Alpha decay, α (proton number  )
Video on α decay
Beta Decay
•Lose beta particle –Electron/beta β
•Negative charge (-1)
•-1 charged (β or electron)
•Daughter nuclei higher in proton number
Decay depend on ratio neutron/proton
Neutron/proton ratio HIGH – Neutron rich
– Decay to reduce neutron
-Beta decay β ( Neutron  Proton + electron)
-Ratio decrease 
Video on β decay
Gamma decay
•Lose a γ particle – electromagnetic radiation of high
frequency
•Daughter nuclei no change in atomic mass
Decay depend on ratio neutron/proton
Neutron/proton ratio HIGH /LOW
-Gamma decay γ, is associated along
with Alpha and Beta
Video on γ decay

8. Isotopes
Unstable Isotopes
Stable Isotopes
Simulation isotope 1H, 2H, 3H
Simulation isotope 12C, 13C, 14C
Emit radiation form unstable isotope
Simulation half life C-14/uranuim
Unstable Isotopes – emits radiation

RADIOISOTOPES
Half-life
Radioisotopes
•Half-life – time taken for conc/amt isotope
to fall to half of its original value.
•Half life decay – always constant
Radioactive isotopes
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
www.sciencelearn.org.nz
Half-life
1.5 x 10-4
Long half-life
More stable, decay slowly
Video on Half life
Shorter half-life
More unstable, decay fast

9. Carbon – 3 Isotopes
Carbon -12
Carbon -13
Abundance – 99% (Stable)
Radiocarbon/carbon dating
Carbon -14
Abundance – 1% (Stable)
Abundance – trace amt
(Unstable , radioactive)
How it is form?
• Half life C-14 = 5730 years
• Beta (β/electron ) decay
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)
Uses
• Age dead organic material/fossil contain Carbon element
• Max age limit is 60,000 years old.
Conclusion
Ratio C14/C12 is constant is organism alive
Ratio C14/C12 drop  organism die

10. How Radiocarbon dating works?
Radiocarbon/carbon dating
Carbon -14
Abundance – trace amt
(Unstable , radioactive)
• Half life C-14 = 5730 years
• Beta (β/electron ) decay
Simulation C-14 (Half life)
At 100% (Starting)
Simulation C-14 (Half life)
At 50% (Starting)
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.
Click to view simulation
•Ratio C14/C12- constant if alive – TAKE in C14 (C12 constant)
•Ratio C14/C12- drop if dead - NOT taking C14. (C12 constant)
Video on Radiocarbon dating
Video on C-14 Carbon Dating
Video on C-14 Carbon Dating/Fossil
Video on C-14 Half life Carbon Dating

11. Uses of radioactive isotopes
Radiocarbon/carbon dating
Carbon -14
Beta (β/electron) decay
Carbon dating
Age of fossil remains
• Half life C-14 = 5730 years
How Radiocarbon dating works?
Radiotherapy/cancer/tumour
Tracers/studying metabolic pathways
Cobalt-60
Iodine-131
Gamma γ + β decay
Gamma γ + β decay
Sterilization – killing bacteria/germ
Radiotherapy – kill tumor cells
High energy electromagnetic ray
•
•
•
Radio tracer
Trace the pathway in body
Beta β (90%) and γ (10%) decay
• Half life Co-60 = 5.27 years
• Half life I-131 = 8 days
How Gamma rays works?
How Radio tracer works?
Video on Radiocarbon dating
Video on C-14 Carbon Dating
Video on Radiotherapy
Video on Radio tracer

12. Atomic /Mass number
No isotopes are present
Proton number = proton
Mass number = proton + neutron
Z
A
6 protons
6 protons + 6 neutrons
8 protons
8 protons + 8 neutrons
Atomic Weight
With isotopes present
Proton number = proton
Z
Mean relative mass (atomic weight)
A
Video on weighted average

13. Relative Atomic Mass
No isotopes are present
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
Proton number = proton
Z
A
Mass number = proton + neutron
Mass number ≠ Average atomic mass
(atomic mass unit)
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)
6
Carbon-12 as standard
1/12 of C12 = 1 unit
6 protons + 6 neutrons
1/12 x
1 unit
=
12
16
16 protons + 16 neutrons
32 unit
32
Sulphur – 32x heavier
Assuming No isotopes present!
http://www.tutorvista.com/content/science/science-i/atoms-molecules/atom.php

14. Relative Molecular Mass
No isotopes are present
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
Mass number ≠ Average atomic weight
(atomic mass unit)
Proton number = proton
Z
A
Mass number = proton + neutron
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)
Carbon-12 as standard
1/12 of C12 = 1 unit
6 protons + 6 neutrons
1/12 x
1 unit
=
8 protons + 8 neutrons
16 unit
2 protons
+ 2 unit
18 unit
H2O – 18x heavier
Assuming No isotopes present!
http://www.tutorvista.com/content/science/science-i/atoms-molecules/atom.php

15. Relative Isotopic Mass
Proton number = proton
Mass number = proton + neutron
Presence of isotopes
Z
A
Z = 29 protons
A
Z
A= 29 protons + 35 neutrons = 64
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 .
Isotopes
X - No isotopes
Y - TWO isotopes
3
CI - TWO isotopes
11
Relative Abundance
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
17
17
35
37
Relative Abundance
75%
25%
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
3
10
3
11
50%
50%
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

16. Relative Atomic Mass
Isotopes are present
Why RAM is not a whole number?
12
Relative Abundance
98.9%
13
1.07%
RAM = 12.01
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
RAM, C :
= (Mass 12C x % Abundance) + (Mass 13C x % Abundance)
= (12 x 98.9/100) + (13 x 1.07/100) = 12.01
Video on Isotopes
Video on weighted average
Video on Isotopes
http://www.tutorvista.com/content/science/science-i/atoms-molecules/atom.php
RAM calculation
Weighted average calculation

17. Relative Atomic Mass
Mg - 3 Isotopes
Relative Abundance
% Abundance
Convert relative abundance to % abundance
24 Mg
– (100/127.2) x 100% - 78.6%
Mg – (12.8/127.2) x 100% - 10.0%
26 Mg – (14.4/127.2) x 100% - 11.3%
25
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
Pb - 4 Isotopes
Relative Abundance
% Abundance
Convert relative abundance to % abundance
204Pb
– (0.2/10) x 100% - 2%
– (2.4/10) x 100% - 24%
207Pb – (2.2/10) x 100% - 22%
208Pb – (5.2/10) x 100% - 52%
206Pb
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

18. Additional Resources
Periodic Table from webelement
Video on isotopes using mass spec
Simulation C-14 dating (Half life)
Excellent Video Higgs Field (Ted Talk)
Video on Particle Physics (Higgs Field)
Simulation U-238 dating (Half life)
Excellent Video on scale of universe
Video on new particles physics
Simulation on atomic model
Simulation isotope 1H, 2H, 3H
and 12C, 13C, 14C