The strong nuclear force doesn't balance the electrostatic force.
Nucleus
If you are referring to a cell's nucleus than the simple answer is that's not radioactive. Radioactivity occurs when elemental atoms become unstable due to the loss or gain of additional neutrons; these unstable atoms are referred to as radioactive isotopes. If a cell's nucleus were radioactive it would not last very long, its structure and function would quickly degrade and collapse.
the absorption of a free-moving neutron by the atom's nucleus
When a neutron hits the nucleus, it can be absorbed by the nucleus, causing the nucleus to become unstable and possibly undergo radioactive decay. This process can lead to the release of energy, emission of radiation, or transmutation of the nucleus into a different element.
Apparently uranium is the largest atom, with 92 protons and 92 electrons.
An unstable nucleus which decays emitting a neutron.
A nucleus with too few nuetrons is unstable because there are not enough to keep the protons. There must be a certain amount of nuetrons for every element.
The stability of an atom depends on a balance between the numbers of protons and neutrons in its nucleus and also on the total size of its nucleus; atoms with sufficiently large nuclei are inherently unstable. Please see the link.
Increasing the ratio neutrons/protons in the nucleus the atom become unstable.
Transuranium elements are radioactive and unstable; the stability of a nucleus is a problem of nucleon physics.
A stable nucleus is one which will not decay, whereas an unstable nucleus will decay at some point, which cannot be predicted as decay is a random process, by alpha or beta decay.
radioisotope
It isn't really an ELEMENT that is unstable, but an ISOTOPE. That means that in general, for the same element, some atoms will decay, and some will not - the difference being the number of neutrons in the nucleus.
Nucleus
Change from unstable to stable nucleus.
Yes.
it might not be unstable with anything.......