Module 1 - Origin of the Elements

Question 1

Patterns in Element Abundances - Steady Decrease as Atomic Number Increases

Answer 1

• Less the sun produces, the less abundant it is
• Heavier elements can only be formed from stellar nucleosynthesis (s-process) of low-mass stars and explosive nucleosysnthesis

Question 2

Patterns in Element Abundances - Low Abundance of Li, Be, B

Answer 2

• Low production through main nucleosynthetic processes, used up in other reactions
• Bulk produced by cosmic ray spallation in interstellar space at low Temp (Galactic Nucleosynthesis
• Cosmic Rays split C,N,O nuclei to produce Li, Be, B

Question 3

Patterns in Element Abundances - Up/down trend

Answer 3

• Oddo-Harkins Rule
• Even numbered elements are more abundant than odd-numbered elements
• Elements most stable when protons are paired
• Full shells are more stable

Question 4

3 lines of evidence for elemental abundance - The sun and spectral analysis

Answer 4

• Elements absorb specific wavelengths, get excited, then jump to higher orbitals
• Can model concentrations from dips in specific wavelengths

Question 5

3 lines of evidence for elemental abundance - Carbonaceous Chondrite Meteorites

Answer 5

• Carbonaceous means contains carbon
• Chrondrites means contains chondrules which are small spheres of crystals and glass, in a silicate-metal-sulfide matrix
• Represent primitive material left over form solar system formation
• Give average composition of solar system
• Matches solar abundances well

Question 6

Helioseismic Data

Answer 6

• Measures sunquakes formed by sound waves in sun
• Indicates heavier elements have settled in centre of sun, lighter ones on outside
• Indicated more metals, solar abundance crisis

Question 7

Isobars

Answer 7

Same mass number

Question 8

Isotones

Answer 8

Same neutron number

Question 9

Chemical reactions

Answer 9

• Compounds formed

Question 10

Nuclear Reactions

Answer 10

• Elements formed
• Spontaneously occur when nuclei are unstable
• Balance between strong nuclear force and electrostatic repulsion
• Require or release loads of energy, way more than chemical reactions

Question 11

Big Bang Nucleosynthesis

Answer 11

• Main source of H and He
• Fusion releases energy but has high activation energy

Question 12

Stellar Nucleosynthesis

Answer 12

• Nuclear Fusion of H to He
• Bigger stars can make bigger elements
• CNO cycle
• Fusion stops at Fe because it has the highest binding energy per nucleon (thermodynamically favourable)
• s-process (slow) in low-mass stars can produce heavier elements

Question 13

Explosive Nucleosynthesis

Answer 13

• r-process (rapid) during a star’s death (supernovae)
• minor p-process, photodisintegration during suvernova