How many atoms are represented in the formula in a small 2HPO small for would it be for 86 or seven?

The chemical formula \( \text{H}_2\text{PO}_4^- \) (which you likely meant with "2HPO") represents the dihydrogen phosphate ion. To count the total number of atoms in this formula, we can break it down:

- \( \text{H} \): 2 atoms of hydrogen
- \( \text{P} \): 1 atom of phosphorus
- \( \text{O} \): 4 atoms of oxygen

Adding these together gives a total of:

\[
2 \, (\text{H}) + 1 \, (\text{P}) + 4 \, (\text{O}) = 7 \text{ atoms}
\]

So, the total number of atoms in \( \text{H}_2\text{PO}_4^- \) is **7**.