How many electrons are needed to consider a element stable

The nucleus of an atom is made up of protons and neutrons. The forces inside the nucleus of a stable atom are balanced because the nucleus contains the proper number of protons and neutrons. These atoms are theoretically resistant to all forms of decay except proton decay, which is a hypothetical form of decay that has never been observed in a laboratory or in nature.Unstable atoms are radioactive and decay after a certain amount of time. Different unstable atoms decay through different processes, such as the ejection of a proton or a neutron; the conversion of a proton to a neutron or a neutron to a proton; and the emission of the excess energy in the form of photons. In many cases, the resulting atom is still unstable. This atom then decays again to a new atom. The process continues in a decay chain until a stable form

The answer would be abrasion.