4.4-4.5: Chain Reactions & Photochemistry Flashcards
Free radicals (⦁)
atoms/molecules w/ unpaired e-
are free radical highly reactive
YES- w/ short life
how do free radicals gain stability?
Gains stability by pairing w/ e- on another atom (covalent bonding)
Free radical formation reaction
(⦁) forms new bond at expense of already existing bond
- New radical attacks another molecule, forms new radical
- A⦁ + B-C –> A-B + C⦁
Chain termination reaction
pair of radicals find each other = form stable molecule
- A⦁ + C⦁ A-C
Catalyzed chain reaction
radical chain reaction circumvents kinetic barrier
Initiation event
produces initial population of radicals
- Required to start radical reactions
- Somehow bond breaks –> fragments of unpaired e-
Atmospheric chemistry is governed by ___ produced by ____
- free radicals
- solar radiation
NOx is an exception to free radicals bc…
it’s still stable (even though has unpaired e-) bc… unpaired e- = in low-energy molecular orbit
Spectrum
variation of light intensity w/ wavelength
spectrum: visible light
wavelength = 400-750 nm (violet –> red)
spectrum: ultraviolet light (UV)
wavelength = < 400 nm
spectrum: infrared light (IR)
wavelength = > 750 nm
Most of suns rays = w/in _______ light region
visible
Solar Spectrum:
Records light arriving @ earth’s surface on clear day
- Sun emits more UV-rays (absorbed by stratospheric ozone layer)