This question seems surprisingly common on the internet; is it a typical homework question?
Beryllium has two electrons in its outer shell and it prefers to shed them, giving a net charge of +2. Usually, though, Beryllium forms covalent bonds rather than ionic bonds. See https://www.quora.com/What-causes-Beryllium-to-not-form-ions-and-Lithium-to-form-ions
That's the "chemistry" answer.
The "physics" version of this answer is "what charge do you want it to have?" It's physically possible to remove just one electron, or all four. It's possible to add electrons, too. You just don't tend to see those configurations in nature.