Doesn't matter, 8 planets instead of 9. At one point I thought there were 7.
8 like the outer valence electrons of P,D,and F shells. Maybe that's why they did it? Something about changing the definition of what a planet is? This is the short answer going by google search as to why they change Pluto's classification:
"Pluto is now classified as a dwarf planet because, while it is large enough to have become spherical, it is not big enough to exert its orbital dominance and clear the neighborhood surrounding its orbit."
A person might say our solar system with eight planets would most well resemble Oxygen, which is non other than number 8. You've have to make a bit of a lead and say the first two planet closest to the sun take up the first shell and six electron remain for the next shell that has a total occupancy of 8 shells. Oxygen is the most abundant element on Earth.
If you said Pluto was one of the electrons then I guess our solar system would then best resemble Florine.
If you just said all 8 planets were valence electrons, then I guess the solar system would most well resemble Neon.
It is strange the solar system ended up looking so much that same as the theoretical model of atoms. Finding similarities from our microcosm to our macrocosm would be exciting, though there doesn't seem to be must other than their appearances to support this idea.
Video Provided By You Tube Channel (LifesBiggestQuestions) --->
Interesting video, a bit abstract, but thought provoking.
I kind of liked 7 like the days of the week, the color spectrum, the musical scale, Tetris pieces and the most likely result from 2 six sided dice. If you break a mirror they say you get 7 years bad luck. Seven really seems to be the number of chaos. In Chemistry the Halogen series have seven Valence electrons, so they tend to share electrons or seek to steal electrons.
9? What would you have compared 9 to? The top of the one's column?
