Why is the correct name of compound Silicon Pentoxide and NOT Silicon Pentoxide ?

If two vowels appear next to each other, the vowel from the Greek prefix (prefixes are your mono, di, tri, penta etc.) is dropped.

Explanation:

If you are looking for why it's Silicon pentoxide and not Silicon pentaoxide, the answer is quite simple.

If two vowels appear next to each other, the vowel from the Greek prefix (prefixes are your mono, di, tri, penta etc.) is dropped.

This is primarily done to easily pronounce the words with clarity. Which is why you'll likely encounter:

- monooxide written as monoxide  (extra o from prefix is gone)

- tetraoxide becomes tetroxide

- pentaoxide becomes pentoxide (this is why it's pentoxide and NOT pentaoxide)