Fantastic Five Facts

I am reading The John W. Campbell Letters. In a letter from 1953 to Ray Jones (fan and sf writer), Campbell outlined the following interesting things about the number 5.

1. Atomic mass-numbers run over 240. In the whole range from 1 to 240-plus, there is one and only one vacant mass number. No atom has a mass of 5.
2. Crystallographers say that no crystal can have five-sided symmetry.
3. Topologists find that no plane or spherical map needs more than 4 colors.
4. Two soap bubbles intersect to form a plane interaction zone. Three intersect in a line. Four meet in a point. But five can't meet.
5. According to Bode's law there should be a planet between Mars, the fourth planet, and Jupiter, the fifth. There's shattered debris instead.
6. But a star fish has pentagonal symmetry. Primitive land-life started with pentagonal pes and manus. Man retained these. We have a pentagonal design.
7. Life is distinguished from the non-living by existing only so long as it is unstable.
8. Magic, down the ages, held the pentagon and the pentacle (five-pointed star) to have mystic powers.
9. Question: What's with the peculiar number Five?