Assigning Oxidation States: Rules & Lewis Structures

In summary, there are two main methods for assigning oxidation states in compounds - drawing Lewis structures and following specific rules. However, as a beginner in chemistry, these methods may not always work for all compounds. As you advance in chemistry, you will learn more rules and methods for assigning oxidation numbers. Some additional methods include using half-reaction equations, knowledge of common elements and their oxidation states, and using a periodic table. Certain elements also have characteristic oxidation states that can be used as a guideline. With these methods, you should be able to assign oxidation numbers to most compounds.
  • #1
Omid
182
0
The book I'm reading, has suggested to methods for assigninig the oxidation statetes in a compound. The first method includes drawing the Lwis structure of the compound. And the second one is based on some rules.
As I'm a beginner in chemsitry there are so many compounds which I can't draw it's Lwis structure. So the first method doesn't work always (for me as a biginner). And in the list of the rules there is no rule for so many situations. For example for these compounds I don't know what to do:
AlCl(3),
ICl,
MgSO(4)
I want to know what will happen. Will I find some more rules as I advance in chemistry?
 
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  • #2
Is there any other method for assigning oxidation numbers?Yes, as you advance in chemistry, you will learn more rules to assign oxidation numbers. In addition to the two methods you mentioned, there are a few other methods that can be used to assign oxidation numbers. These include the use of half-reaction equations and the knowledge of common elements and their oxidation states. You can also use a periodic table to help determine oxidation states. Furthermore, certain elements have characteristic oxidation states that can be used as a guideline. For example, oxygen is usually -2, hydrogen is +1, and chlorine is -1. Using this information and the other methods mentioned, you should be able to assign oxidation numbers to most compounds.
 
  • #3


It is common for beginners in chemistry to struggle with assigning oxidation states, as it requires a solid understanding of molecular structures and chemical bonding. Drawing Lewis structures can be a helpful tool, but as you mentioned, it may not always be feasible for every compound.

Fortunately, there are some general rules that can be applied to assign oxidation states. These rules are based on the electronegativity of the elements involved in the compound, as well as their oxidation states in known compounds.

For example, in compounds like AlCl3 and ICl, the electronegativity difference between Al and Cl, and I and Cl, respectively, can help determine the oxidation state of each element. In general, the more electronegative element will have a negative oxidation state, while the less electronegative element will have a positive oxidation state.

In the case of MgSO4, the oxidation state of Mg can be determined by considering the overall charge of the compound (which is 0) and the known oxidation states of the other elements (S in this case has an oxidation state of +6). This means that Mg must have an oxidation state of +2 to balance out the overall charge.

As you continue to study chemistry, you will learn more about the properties of elements and how they affect their oxidation states. This will help you develop a better understanding of how to assign oxidation states in more complex compounds. Additionally, practicing with different compounds and seeking help from your teacher or classmates can also improve your skills in this area.

Remember, assigning oxidation states is not an exact science and there may be exceptions to the rules. However, with practice and a solid understanding of chemical bonding, you will become more confident in assigning oxidation states.
 

Related to Assigning Oxidation States: Rules & Lewis Structures

1. What are oxidation states and why are they important in chemistry?

Oxidation states, also known as oxidation numbers, are a measure of the degree of oxidation of an atom in a molecule or ion. They indicate the number of electrons that an atom has gained or lost in order to form a chemical bond. This is important in chemistry because it allows us to predict the reactivity and behavior of molecules, as well as track the transfer of electrons in chemical reactions.

2. What are the rules for assigning oxidation states?

There are several rules for assigning oxidation states, but the most commonly used ones are:

  • The oxidation state of an uncombined element is always 0.
  • The oxidation state of a monatomic ion is equal to its charge.
  • The oxidation state of oxygen in most compounds is -2, except in peroxides where it is -1.
  • The oxidation state of hydrogen in most compounds is +1, except in metal hydrides where it is -1.
  • The sum of oxidation states in a neutral molecule is always 0, and in an ion it is equal to the charge of the ion.

3. How do I determine the oxidation state of an element in a compound?

To determine the oxidation state of an element in a compound, you can follow these steps:

  1. Identify the overall charge of the compound.
  2. Use the rules for assigning oxidation states to determine the oxidation state of the element in the compound.
  3. Check if the sum of oxidation states in the compound is equal to the overall charge.

4. How do oxidation states relate to Lewis structures?

Oxidation states can be used to determine the placement of atoms in Lewis structures. The more electronegative atom in a bond will have a negative oxidation state, while the less electronegative atom will have a positive oxidation state. This can help in drawing the correct Lewis structure for a molecule.

5. Can oxidation states change in a molecule?

Yes, oxidation states can change in a molecule through chemical reactions. This is because during a reaction, electrons can be transferred from one atom to another, resulting in a change in oxidation state for those atoms. However, the overall sum of oxidation states in a molecule will always remain constant.

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