system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How is oxygen (O2) odorless but ozone (O3) smells and is hazardous?
gpt
O2 and O3 have different chemical structure (bond angle, length, spatial orientation etc)  which give them different physical and chrmical properties.

Just like graphite, diamond and fullerene are pure Carbon but have drastically different properties.