The oxidation number of phosphorus in ATP (adenosine triphosphate) is

Options

A. 4
B. 3
C. 5
D. 2

Answer

To find the oxidation number of phosphorus in ATP (adenosine triphosphate), we can follow these steps:

### Step 1: Understand the Structure of ATP
ATP consists of three phosphate groups, a ribose sugar, and an adenine base. The focus here is on the phosphate groups, which contain phosphorus (P) and oxygen (O).

### Step 2: Identify the Phosphate Group
The phosphate group can be represented as \( PO_4^{3-} \). In this group, phosphorus is bonded to four oxygen atoms.

### Step 3: Assign Oxidation States
The oxidation state of oxygen is typically \(-2\). Since there are four oxygen atoms in the phosphate group, their total contribution to the charge is:
\[ 4 \times (-2) = -8 \]

### Step 4: Set Up the Equation
Let the oxidation number of phosphorus be \( X \). The overall charge of the phosphate group is \(-3\). Therefore, we can set up the equation:
\[ X + (-8) = -3 \]

### Step 5: Solve for X
Rearranging the equation gives:
\[ X - 8 = -3 \]
\[ X = -3 + 8 \]
\[ X = +5 \]

### Conclusion
The oxidation number of phosphorus in ATP is \( +5 \).