What is the chemical formula for the ionic compound formed by Au3+ and
HSO3-?

The chemical formula for the ionic compound formed by Au3+ and

HSO3-compound  is Au(HSO3)3

Explanation:

The charge on Au ion is

And the charge on HSO3- is

Thus, the number of atoms required by HSO3- to complete its octate is 1. On the other hand Au has 3 excess ions and hence it is to be released to reach the stable state.

So three molecules of HSO3- will combine with one atom of Au 3+

Thus, the compound formed by these two is Au(HSO3)3

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.