What is the name and formula of the principal aluminium compound in it?

The compound of aluminium is aluminum trioxide. The compound is having molecular formula as Al₂O3.

In this compound, aluminium is having oxidation state 3 while oxygen is having oxidation state 2. It is formed as valency of aluminium is 3 while oxygen is 2. So the compound is having molecular formula as Al₂O3.

It is most common compound of aluminium.

pla·gia·rism

/ˈplājəˌrizəm/

learn to pronounce

noun

the practice of taking someone else's work or ideas and passing them off as one's own.

explanation:

answer; talc and gypsum;