Here's how you can write a formula when you have three times as many hydrogen atoms as phosphorus atoms:

1. Understand the Relationship:

* The problem states that for every one phosphorus atom (P), there are three hydrogen atoms (H).

2. Represent with Variables:

* Let 'x' represent the number of phosphorus atoms.

* Since there are three times as many hydrogen atoms, the number of hydrogen atoms will be '3x'.

3. Write the Formula:

* The formula will be H_3xP_x

Example:

Let's say you have 2 phosphorus atoms (x = 2):

* Hydrogen atoms: 3 * 2 = 6

* Formula: H₆P₂

Important Note:

This formula represents the ratio of hydrogen to phosphorus atoms. You can simplify the formula by dividing both subscripts by the smallest subscript (in this case, 'x') to get the simplest whole-number ratio. However, the original formula (H_3xP_x) still accurately reflects the 3:1 ratio.