What is a radical?

• A species with an unpaired electron
• A stable ion with a full outer shell
• A molecule that cannot react

What does ultraviolet light do to a chlorine molecule?

• It joins two molecules together
• It splits it into two radicals
• It removes all the electrons

Which step ends a radical chain?

• Propagation
• Initiation
• Termination

Why does one photon lead to many product molecules?

• Light keeps shining the whole time
• The chain regenerates its radical
• Termination creates new radicals

For ethane with chlorine, which is the first propagation step?

• Cl radical plus C2H6 gives HCl plus an ethyl radical
• C2H6 plus Cl2 gives two molecules of HCl
• Ethyl radical plus C2H6 gives butane plus hydrogen

Further substitution can be avoided, so the flask holds pure chloromethane.

Why do chlorine radicals from old refrigerants destroy many ozone molecules each?

• Each radical is regenerated in a chain
• Ozone molecules break down on their own
• Termination multiplies radicals

A student writes propagation without any dots and says the steps still balance. What is wrong?

• Dots are decoration and can be dropped
• The dots show where the radicals are
• Dots belong only on stable molecules