2. Nuclear Chemistry

Question 1

What are the three types of ionizing radiation?

Answer 1

α (emission of He nucleus)

β (emission of e)

γ (type of electromagnetic radiation)

Question 2

What are the other partciles that can be emitted despite the three types of radiation?

Answer 2

Positrons (β⁺) - like e but positively charged

Neutrinos (ν) - low mass particle

Question 3

Explain alpha emission

Answer 3

• In alpha mession an alpha particle is lost (He nucleus)
• Atomic mass decreases by 4
• Atomic number decreases by 2
• E given out E=mc²

Question 4

Explain beta emission

Answer 4

• beta emission - loss of an e from the nucleus
• mass number unchanged
• atomic number increases by 1

Question 5

Explain gamma emission

Answer 5

• gamma radiation is emitted with / after alpha / beta radiation when the new nucleus is formed is in an excited state
• excited states (less stable) are denoted by m

E = hv (for gamma radiation E)

Question 6

What are transuranic elements?

Answer 6

• elements after U - not naturally occuring
• can be made by smashing two nuclei together in a partcile accelerator

Question 7

How do decay series look?

Answer 7

alpha decay: atomic mass decreases by 4, atomic # decreases by 2

beta decay: atomic mass unchanged, atomic # increases by 1

Question 8

What is nucleosynthesis? What are the types?

Answer 8

Nucleosyntehsis - process of making the elements

Tends to go in stars, takes several processes

1. Big bang nucleosynthesis
2. Stellar nucleosynthesis
3. Supernova nucleosynthesis

Question 9

Explain big bang nucleosynthesis

Answer 9

Big bang theory indicates H and He were formed within first few minutes when the Universe was formed -> produced ¹H, ²H, ³H, ³He, ⁴He, ⁷Li

Mechanism: fusion of protons + neutrons + small nuclei

Common mechanism - proton-proton chain mechanism

Question 10

What is proton-proton chain mechanism?

Answer 10

Question 11

Explain stellar nucleosynthesis

Answer 11

Stellar nucleosynthesis - heavier lemenets not formed in big banh - fomred in stars

By nuclear fusion where 2+ nuclei react

Depends on temperature and mass of stars

Question 12

Why do decays stop at iron?

Answer 12

⁵⁶Fe the most stable nucleus - binding E after Fe decreases - E must be put in to crash nuclei together (instead of released) - more difficult - extra E needed

Question 13

Explain supernova nucleosynthesis

Answer 13

Supernova nucleosynthesis - situation where lots of E can be obtained for fusion of elements heavier than Fe - free neutrons interact with heavier nuclei - much E produced by explosion of stars

• r-process and s-process

Question 14

Nucleosynthesis periodic table

Answer 14