It all depends on how many pendants you want to have. for a 90" island you probably want 3-5 pendants. An odd number of pendants over an island works best.

Let's say in your case the island is 90" and you want to have 3 pendants- 10" diameter each. Combined all diameter will be 30"... 90"-30"=60"

3 pendants+1 =4 (number of spaces in between the lights and ends of the island.

Now take 60/4=15" that will give you the distance between each light.

This is just an example:

Layout

How it will look in reality.

You can go with 3-12" pendants and reduce space in between, or put smaller pendants over the overhang area if you have it and add a few recessed lights over the main area, or you can put 2 larger pendants but that would be more like mini chandeliers, over the entire area. There is a few ways this can be done depends on the look you want to have.

Good luck