To determine which element has been oxidized in the redox reaction \( \text{AgNO}_3 + \text{Na} \rightarrow \text{NaNO}_3 + \text{Ag} \), we need to identify the changes in oxidation states of the elements involved in the reaction. Oxidation involves an increase in the oxidation state of an element, while reduction involves a decrease in the oxidation state. Let us analyze each element's oxidation state before and after the reaction.
1. Sodium (Na):
- In the reactant side, sodium is in its elemental form, \( \text{Na} \), with an oxidation state of \( 0 \).
- In the product side, sodium is part of sodium nitrate, \( \text{NaNO}_3 \). Here, sodium typically has an oxidation state of \( +1 \).
2. Silver (Ag):
- In the reactant side, silver is part of silver nitrate, \( \text{AgNO}_3 \). Here, silver has an oxidation state of \( +1 \).
- In the product side, silver is in its elemental form, \( \text{Ag} \), with an oxidation state of \( 0 \).
3. Nitrogen (N) and Oxygen (O):
- The oxidation states of nitrogen and oxygen in \( \text{AgNO}_3 \) and \( \text{NaNO}_3 \) remain the same as both are in the nitrate ion (\( \text{NO}_3^- \)). Typically in nitrate ions, nitrogen has an oxidation state of \( +5 \) and oxygen has an oxidation state of \( -2 \).
Now, comparing the changes in oxidation states:
- Sodium (Na) goes from \( 0 \) to \( +1 \), indicating that it has been oxidized.
- Silver (Ag) goes from \( +1 \) to \( 0 \), indicating that it has been reduced.
Given that oxidation is the loss of electrons (increase in oxidation state), the element that has undergone oxidation in this reaction is Sodium (Na).
Thus, the correct answer is:
C. Sodium (Na)
