Yes, a covalent bond can form between hydrogen and phosphorus. This is because both elements can share electrons to achieve a stable electron configuration.

Here's how it works:

* Hydrogen (H) has 1 electron in its outer shell and needs 1 more to complete it.

* Phosphorus (P) has 5 electrons in its outer shell and needs 3 more to complete it.

To form a stable molecule, phosphorus shares its electrons with three hydrogen atoms. This results in the formation of phosphine (PH₃), a colorless, toxic gas.

Here's a simple diagram:

```

H

|

H - P - H

|

H

```

Each line represents a shared pair of electrons (a single covalent bond).

Important Note: While covalent bonds between hydrogen and phosphorus are possible, they are relatively weak compared to other covalent bonds. This is due to the significant difference in electronegativity between hydrogen and phosphorus.