Iron exists in several oxidation states, represented by Fe$II$ and Fe$III$ in the compounds FeCl2 and FeCl3 respectively.

FeCl2, also known as iron$II$ chloride, is a greenish-yellow solid that is soluble in water. FeCl3, or iron$III$ chloride, is a brownish-red solid that is also soluble in water.

FeOH2 is iron$II$ hydroxide, a greenish solid that is sparingly soluble in water. FeOH3 is iron$III$ hydroxide, a reddish-brown solid that is insoluble in water.

FeSO4 is iron$II$ sulfate, a white solid that is soluble in water. Fe2$SO4$3 is iron$III$ sulfate, a yellowish solid that is also soluble in water.

In summary, the compounds listed in the sequence Fe-FeCl2-FeOH2-FeSO4-FeCl3-FeOH3-FeSO4 represent different oxidation states of iron and its corresponding compounds.