Final answer:
In H2O, the oxidation number is +1 for each hydrogen and -2 for each oxygen, regardless of the quantity of water molecules. Therefore, in 7H2O, each hydrogen still has an oxidation number of +1, and each oxygen has an oxidation number of -2, and these values don't change with the quantity.
Step-by-step explanation:
The oxidation number of hydrogen (H) in H2O is +1 and for oxygen (O), it is -2. Thus, in the case of 7H2O, the oxidation number for each hydrogen remains +1 and each oxygen remains -2. In a molecule of H2O, there are two hydrogens and one oxygen, so when water is in pure form or not part of a more complex molecule or ion, its overall charge is neutral, and the oxidation numbers of all the atoms will add up to zero. This concept is crucial for understanding redox reactions, where transfer of electrons is involved.
It's important to note that even if the question asks for 7H2O, the quantity of water molecules does not affect the oxidation numbers of the individual atoms within each water molecule. Therefore, regardless of whether there is one molecule of water or seven, the oxidation numbers in each individual molecule of H2O remains the same.