Borek said:In general you should compare potentials of half reactions. In this case go for Cr3+.
A valence state is the number of electrons an atom has in its outermost energy level. It is important because it determines how an atom will react with other atoms to form chemical bonds.
The valence state of an atom can be determined by looking at its position on the periodic table. The group number of the element corresponds to its valence state.
Yes, some atoms can have multiple valence states. This is typically seen in transition metals, which can have different valence states depending on the reaction they are involved in.
The valence state of an element can affect its chemical reactivity and the types of compounds it can form. For example, elements with a full outer energy level (valence state of 0) are typically unreactive, while elements with a partially filled outer energy level (valence state of 1-7) are more reactive.
Yes, there are exceptions to the valence state rule. Some elements, such as the noble gases, have a full outer energy level and are typically unreactive, but can form compounds in certain circumstances.