Using stock notation represent the following compounds :
(i) `HAuCl_4` (ii) `Tl_2O` (iii) FeO (iv) `Fe_2O_3`
(v) CuI (vi) CuO (vii) MnO (viii) `MnO_2`

Explanation

To represent the given compounds using stock notation, we need to determine the oxidation states of the elements in each compound and then write the formula with the oxidation state in Roman numerals. Let's go through each compound step by step.

### Step-by-Step Solution:

**(i) `HAuCl_4`**

1. Identify the oxidation state of Au (Gold). Let it be \( x \).
2. Chlorine (Cl) has an oxidation state of -1, and there are 4 Cl atoms.
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