It truly IS a personal preference, however the most important question is what do the pendants hold for light bulbs? If they hold a 100 watt medium based bulb (max), you should have enough light. I would place the pendants 36" from each other and leave 20.5" from each end. This in my humble opinion is the MAX spacing for a small pendant. Could you draw and cut out 3 pieces of paper or cardboard and place them on the island for a visual for yourself? This always helps! :)

An addendum to that would be: I usually place small pendants like that about 24" apart, however, then it calls for 4 lights and designers would rather see odd numbers. If using 4, I would space them about 28" apart, leaving approx 15" on either end. You will possibly get lots of comments on everyone's thoughts, because again, it is truly a personal preference. :)

Thank you Illuminations Lighting for your reply and advice. I am wondering if your math is correct in your first answer? To confirm our island is 113 X 42 inches. I placed three 8 inch plates on the island in the spots where the roughed in electrical has been done. The distance between the lights would be about 23 inches and 21 inches at the ends of the island. I won't be able to go with 4 pendants as the cost of getting the electrician back to change it plus the Drywaller costs are high. So my decision is whether to keep the three 8 inch lights or return them to Restoration Hardware and buy the 14 inch version. The Clemson Classic comes only in 8, 14 and 18 inches. If we switch to the 14 inch pendants there would be approx 16 inches in between the lights (edge to edge) and about 18.5 from the outside lights to the end of the island. I am leaning towards going to the 14 inch size. Appreciate feed aback form you and other pros!! Thank you so much.

Depending on your and other heights, the 14" maybe too big and one leaning over to dice and chop may bang their head on them.

What a beautiful kitchen! That is a long island! I think you're going to have to bite the bullet on spacing the lights. You can get a rail installation that allows you to add as many lights as you want and space them accordingly. If you put the rail centered over the island you could have five or more small ones. That way there isn't a lot of drywall issues. They are hook up to one source. It doesn't look like the spacing is currently correct for three lights. You could return the RH lights and find some that will work in this application.

Ah yes, but I always measure "on center" :) IMHO I think both would look great! A good argument for the larger would be: Remember the single Island lights that have 3 globes on them and install on one junction box? Those globes are anywhere from 3" - 10" apart from each other. I don't think you can go wrong either way! And post a picture of the pendant! I'd love to see them. :) UPDATE: Never mind, I see you said Clemson Classic in your post! ;)

Thanks suzyq for your advice. I am pretty stuck on the Clemson Classic pendants by RH as I researched what I wanted for weeks and weeks and we are not fans of the single track lights as shown in your photo. And using Houzz has been an invaluable tool during this kitchen/bathrooms renovation.
Illumination Lighting I will go back and remeasure now that I know you use centre to centre and not edge to edge!

I looked at the Clemson Classic. Very pretty! The 14" takes 2 bulbs. If you need more light, go for the it. Your space can do either. I'd put them on a dimmer for sure if you go big.

KamyLes13, our island is 100"L. We went w/ cylindrical pendants by Tech Ltg. that are 8.8"Hx4.5"W & they look fine. Given sight lines in your K, I don't think you want ones any bigger than what you're considering. BTW, we went w/ LED bulbs for a couple reasons, one being I didn't want incandescent that some bureaucrat could outlaw in the future, obsoleting my investment.