Ye olde Bohr atom. It's crude compared to the best modern physics explanations, but it is an easy to understand approximation -- and it can make very attractive little spin toys. My daughter saw Thing 114247 and asked me to print some as a gift for her Physics teacher (spelling out P H Y Si Cs). However, 114247 uses pre-discovery names for four elements, is one-sided, chunky (slow to print), didn't have an integrated mount, and was likely to not spin freely... so I was inspired to create this better model.

This design is larger, but two-sided, prints faster fully assembled without supports, and you can turn the parts by simply blowing on it. It can be printed with an optional integrated hanger or stand. Here's a movie of the Si model spinning as a hair dryer is pointed at it from a foot away: https://youtu.be/Tz-r02JZf98