1) in periodic acid (HIO₄), iodine has oxidation number +7, hydrogen has oxidation number +1, oxygen has -2, compound has neutral charge:
+1 + x + 4 · (-2) = 0.
x = +7.
2) in molecule of iodine (I₂), iodine has oxidation number 0, because iodine is nonpolar molecule.
3) in sodium iodide (NaI), iodine has oxidation number -1, sodium has oxidation number +1: 
+1 + x = 0.
x = -1.
4) in iodic acid (HIO₃), iodine has oxidation number +5, hydrogen has oxidation number +1, oxygen has -2, compound has neutral charge:
+1 + x + 3 · (-2) = 0.
x = +5.
        
                    
             
        
        
        
First, we calculate of the concentration of the H+ ions in the solution from the pH given. Then, calculate the new concentration after dilution. Calculation are as follows:
pH = -log[H+]
5 = -log[H+]
[H+] = 1 x 10^-5 M
M1V1 = M2V2
<span>1 x 10^-5 M (V1) = M2(100V1)
</span>M2 = 1 x 10^-7
pH =  -log[<span>1 x 10^-7</span>]
pH = 7
        
                    
             
        
        
        
Polyatomic ions:  ,
,  ,
,  ,
,  ,
,  , and
, and 
Monatomic ions:  ,
,  , and
, and 
<h3>Monoatomic vs Polyatomic Ions</h3>
In chemistry, monoatomic ions are ions that consist of only a single type of atom. They are usually positive or negatively charged and are otherwise known as simple ions. Examples include   ,
,  , and
, and 
Polyatomic ions, on the other hand, are ions that consist of more than one atom, unlike monoatomic ions. The two or more atoms are covalently bonded and the entire structure behaves like a single chemical entity in reactions. Polyatomic ions are otherwise known as molecular ions. 
Examples of polyatomic ions are   ,
,  ,
,  ,
,  ,
,  , and
, and 
Thus, from the diagram:
- Polyatomic ions:  , , , , , , , , , and , and 
More on ions can be found here: brainly.com/question/14982375
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