Toward Ecosophy

That's why I differentiate between the material and etheric planes. If you do that, the seven sub-planes of the material plane work out as follows:

7th (lowest): solid matter
6th: liquid matter
5th: gaseous matter
4th: electromagnetism
3rd: gravity
2nd: weak nuclear force
1st (highest): strong nuclear force

In every set of sub-planes, the lower three have the nature of substance, the middle one has the nature of energy, and the upper three have the nature of space. It all works rather nicely. Then in the etheric plane the lower three sub-planes are the chemical ethers, the middle one is the life ether, and the three higher are the light ethers.