What is sum of oxidation number and coordination number of Al in Cryolite?

Answer

To find the sum of the oxidation number and coordination number of Al in Cryolite, we can follow these steps:

### Step 1: Determine the formula of Cryolite
The formula of Cryolite is Na₃AlF₆.

### Step 2: Assign oxidation states
- Sodium (Na) has an oxidation state of +1.
- Fluorine (F) has an oxidation state of -1.
- Let the oxidation state of Aluminum (Al) be x.

### Step 3: Set up the equation
Using the formula Na₃AlF₆, we can set up the equation based on the overall charge being zero:
\[ 3(+1) + x + 6(-1) = 0 \]
This simplifies to:
\[ 3 + x - 6 = 0 \]

### Step 4: Solve for x
Rearranging the equation gives:
\[ x - 3 = 0 \]
Thus,
\[ x = +3 \]
So, the oxidation number of Al in Cryolite is +3.

### Step 5: Determine the coordination number
The coordination number is defined as the number of surrounding atoms (or donor atoms) attached to the metal center. In Cryolite, there are 6 fluorine atoms surrounding the aluminum atom.

### Step 6: Calculate the sum
Now, we can sum the oxidation number and the coordination number:
\[ \text{Sum} = \text{Oxidation number} + \text{Coordination number} \]
\[ \text{Sum} = 3 + 6 = 9 \]

### Final Answer
The sum of the oxidation number and coordination number of Al in Cryolite is **9**.

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