How would you write the formula for sodium perchlorate?

To write the formula for sodium perchlorate, we need to understand the components involved in the compound.

1. **Identify the Ions**:
- **Sodium ion (Na⁺)**: Sodium is an alkali metal and typically forms a cation with a charge of +1.
- **Perchlorate ion (ClO₄⁻)**: Perchlorate is a polyatomic ion consisting of one chlorine atom bonded to four oxygen atoms, carrying a charge of -1.

2. **Combining the Ions**:
- When writing the formula for an ionic compound, the total charge must be neutral. Since sodium has a +1 charge and perchlorate has a -1 charge, they can combine in a 1:1 ratio.

3. **Writing the Formula**:
- The formula is written by placing the cation (sodium) first, followed by the anion (perchlorate). Thus, the formula for sodium perchlorate is:

\[
\text{NaClO}_4
\]

### Summary
- **Sodium ion**: Na⁺
- **Perchlorate ion**: ClO₄⁻
- **Formula**: NaClO₄

This compound consists of one sodium ion and one perchlorate ion, resulting in a neutral compound.