Apple has always had a method of associating accents with their most commonly attached letters.
á é í ó ú are made by typing opt e then the vowel
ä ë ï ö ü are made by typing opt u then the vowel
â ê î ô û are made by typing opt i then the vowel
ñ is made by typing opt n then the letter
There are many more including the Scandinavian å ø which are just the option + the vowel.
The same with ç ß ∂ ƒ µ etc.
Peter