Answer:
3Fe²⁺ and 2Fe³⁺
Explanation:
In a formula unit of crocidolite you have:
2 Si₄O₁₁: Where Si has an oxidation state of +4 and O a of -2. Thus, global oxidation state is: +4×4 + -2×11 = -6. As there are 2 Si₄O₁₁ = -12
2 OH: Where the oxygen has an oxidation state of -2 and H of +1, thus, 2 OH have an oxidation state of -2
2 Na: The sodium has +1 of oxidation state and there are 2, thus: +2
As global oxidation state of crocidolite is 0, The 5 fe must have as oxidation state:
0 = -12 -2 +2 +5Fe → 5Fe = +12
The common oxidation states of Fe are +3 and +2. Thus, if 5 Fe must have an oxidation state of +12, there are 3Fe²⁺ and 2Fe³⁺
