When working with diptongos, we were told that two strong vowels or a strong with an accented weak vowel were the only ways we separated the word into syllables.
For example, the word "cuál" is not separated because the weak "u" and the accented "a" prevent a separation whereas the word "quién" can apparently be separated as "qui|én".
Why is this even though 'i' is a weak vowel and 'é' is a strong?