Using stock notation, represent the following compound and write names also.
`Na_(2)Cr_(2)O_(7)`

Explanation

To represent the compound \( \text{Na}_2\text{Cr}_2\text{O}_7 \) using stock notation and to write its name, we can follow these steps:

### Step 1: Identify the oxidation states of the elements in the compound.
- Sodium (Na) typically has an oxidation state of +1.
- Oxygen (O) typically has an oxidation state of -2.

### Step 2: Determine the total charge contributed by the oxygen atoms.
- In \( \text{Na}_2\text{Cr}_2\text{O}_7 \), there are 7 oxygen atoms.
- The total contribution from oxygen is \( 7 \times (-2) = -14 \).

### Step 3: Calculate the total charge contributed by sodium.
- There are 2 sodium atoms, each with a charge of +1.
- The total contribution from sodium is \( 2 \times (+1) = +2 \).

### Step 4: Calculate the oxidation state of chromium (Cr).
- Let the oxidation state of chromium be \( x \).
- The overall charge of the compound is neutral (0), so we can set up the equation:
\[ 2(+1) + 2x + 7(-2) = 0 \]
\[ 2 + 2x - 14 = 0 \]
\[ 2x - 12 = 0 \]
\[ 2x = 12 \quad \Rightarrow \quad x = +6 \]

### Step 5: Write the stock notation.
- In stock notation, we represent the oxidation state of chromium in Roman numerals.
- The compound can be represented as:
\[ \text{Na}_2\text{Cr}_2^{VI}\text{O}_7 \]

### Step 6: Write the name of the compound.
- The name of \( \text{Na}_2\text{Cr}_2\text{O}_7 \) is sodium dichromate.

### Final Answer:
- Stock Notation: \( \text{Na}_2\text{Cr}_2^{VI}\text{O}_7 \)
- Name: Sodium dichromate

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