Problem 76 - Chemistry: An Atoms-Focused Approach

Question

What is the sum of the oxidation numbers of the atoms in a molecule?

Step-by-Step Solution

Answer

Answer: The sum of the oxidation numbers of the atoms in a water molecule is 0.

Step 1: Define oxidation number

An oxidation number is a positive or negative value assigned to elements in a compound, representing their 'apparent charge'. It indicates the degree of oxidation (loss of electrons) of an atom in a compound.

Step 2: Identify some general rules to assign oxidation numbers

Using the following general rules, you can determine the oxidation number of any atom in a molecule or ion: 1. The oxidation number of an uncombined element is always 0. 2. The sum of the oxidation numbers of all the atoms in a neutral molecule is 0. 3. The oxidation number of a monatomic ion is the same as its charge. 4. Oxygen usually has an oxidation number of -2. 5. Hydrogen usually has an oxidation number of +1. 6. In polyatomic ions, the sum of oxidation numbers equals the charge of the ion.

Step 3: Assign oxidation numbers to atoms in the given molecule

Assign individual oxidation numbers to the atoms in the molecule, using the rules given in Step 2. If the molecule is not provided in the exercise, choose a molecule and apply these rules. For example, let's find the sum of oxidation numbers in the water molecule (H\(_2\)O): 1. Hydrogen has an oxidation number of +1 as mentioned in the rules. 2. Oxygen has an oxidation number of -2 as per the rules. So, the oxidation numbers of the atoms in water are: +1 for each hydrogen atom and -2 for oxygen.

Step 4: Calculate the sum of the oxidation numbers

Add the oxidation numbers of all the atoms in the molecule to find the sum of oxidation numbers. In our example of the water molecule (H\(_2\)O): Sum of oxidation numbers = 2(+1) + (-2) = 2 - 2 = 0 The sum of the oxidation numbers of the atoms in the water molecule is 0.