How do I find oxidation numbers of certain elements in compounds? I'm really confused so very simple terms would be appreciated. EX: What is the oxidation number of sodium in NaOH AND What is the oxidation number of Iron in FeCl3??
To determine the oxidation number of an element in a compound, you need to follow a few rules. I'll explain using your examples:
1. Rule #1: The oxidation number of an element in its elemental state (uncombined) is always zero. This means that the oxidation number of sodium in NaOH is zero.
2. Rule #2: The oxidation number of a monoatomic ion is equal to its charge. In this case, sodium is combined with oxygen to form the hydroxide ion (OH-). Oxygen has an oxidation number of -2, and since the overall charge of the hydroxide ion is -1, the oxidation number of sodium must be +1 to balance the charges. So, the oxidation number of sodium in NaOH is +1.
For the second example:
1. Rule #1 still applies; the oxidation number of an element in its elemental state is zero. Therefore, the oxidation number of iron in FeCl3 is zero.
2. In FeCl3, chlorine has an oxidation number of -1 (since it is a halogen). Since the overall charge of the compound is zero, the oxidation numbers of all the elements must add up to zero. This means that the oxidation number of iron can be calculated by adding up the oxidation numbers of the chlorine atoms.
Since there are three chloride ions (Cl-) in FeCl3, and each one has an oxidation number of -1, the total oxidation number contributed by the chlorine is -3. Therefore, for the oxidation numbers to add up to zero, the oxidation number of iron must be +3.
So, the oxidation number of sodium in NaOH is +1, and the oxidation number of iron in FeCl3 is +3.
In summary, to determine oxidation numbers:
1. For an element alone, the oxidation number is zero.
2. For a monoatomic ion, the oxidation number is equal to its charge.
3. To balance the charges in a compound, consider the oxidation numbers of other elements in the compound and the overall charge.
To find the oxidation number of an element in a compound, you can follow these steps:
1. Start by assuming that the compound is ionic, meaning that electrons are transferred completely from one atom to another.
2. Identify the known oxidation numbers of other elements in the compound. In the case of NaOH, oxygen typically has an oxidation number of -2, as it almost always takes on a negative charge. This means that hydrogen would have an oxidation number of +1, as it usually takes on a positive charge.
3. Since the compound is neutral, with no overall charge, the oxidation numbers of all the elements must add up to zero. In NaOH, the oxidation number of hydrogen is +1, so to balance it out, the oxidation number of sodium must be -1, since 1 - 1 = 0.
4. Now, let's consider FeCl3. Chlorine is usually assigned an oxidation number of -1. Since there are three chlorines, the total oxidation number contribution from the chloride ions is -3. The compound is neutral, so the sum of all the oxidation numbers must equal zero. Therefore, the oxidation number of iron (Fe) must be +3, since +3 + (-3) = 0.
So, in simple terms, the oxidation number of sodium (Na) in NaOH is -1, and the oxidation number of iron (Fe) in FeCl3 is +3.