<u>Answer:</u> The formula of chromic acid is 
<u>Explanation:</u>
We are given an ionic compound named as chromic acid. This acid is formed by the combination of hydrogen ion and chromate ion.
An acid is defined as the substance which releases hydrogen ion when dissolved in water.
Hydrogen is the 1st element of periodic table having electronic configuration of
.
This element will loose 1 electron to form
ion.
Chromate ion is a polyatomic ion having chemical formula of 
By criss-cross method, the oxidation state of the ions gets exchanged and they form the subscripts of the other ions. This results in the formation of a neutral compound.
So, the chemical formula for the given compound is 
Thus, the formula of chromic acid is 
Alright so the way I see it by definition of increasing atomic number of the halogen family, that means you're going down the periodic table. Therefore, there's an increase in the number of outer shells. The atomic radius would increase because that's basically the distance between the nucleus of the element to the outermost electron. More electron shells=Greater distance=Larger atomic radius