I can't help you with the paper because it is to small.
That's actually a polyatomic Ion, so it's an Ionic bond, because Aluminum is a metal, and sulfate is a covalent compound.
Answer:
Using the VSEPR theory, the electron bond pairs and lone pairs on the center atom will help us predict the shape of a molecule. The shape of a molecule is determined by the location of the nuclei and its electrons. The electrons and the nuclei settle into positions that minimize repulsion and maximize attraction.
For example phosphorus and oxygen can covalently bond to form a polyatomic ions, PO4³⁻ and PO3³⁻.
