Precision spectroscopy of helium and other atomic systems is a vital area of research in modern physics ... which is a unique frequency at which the atom does not interact with laser light.

For example, a helium atom has an atomic mass of 4, but an atomic number (or positive charge) of 2. Since electrons have almost no mass, it seemed that something besides the protons in the nucleus ...

The relative charge of a nucleus is the same as its proton (atomic ... charged ion if the atom gains one or more electrons, it becomes a negatively-charged ion A helium atom has two electrons ...

Helium is notoriously hard to contain because, like hydrogen, it is a tiny little atom even by atomic standards ... or gyroscope that is in most modern phones and affect its operation.