A radioactive atom is an atom of an element with an unstable nucleus.
Increasing the ratio neutrons/protons in the nucleus the atom become unstable.
Nucleus
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.
isotope
unstable, radioactive
An unstable atom is an atom that has an imbalance in the ratio of protons to neutrons in its nucleus, making it prone to undergo radioactive decay. This decay results in the emission of particles or energy in order to achieve a more stable configuration. Unstable atoms will continue to decay until they reach a state of stability.
If an atom has more protons then electrons the atom will have a negative charge.If the atom has more electrons then protons the atom will have a positive charge.If the atom has equal numbers of electrons and protons then the atom becomes neutral.However if you're wondering why an atom is stable then that means that it has all the electrons inside of it paired. If the atom is unstable it has unpaired electrons.
Radioactivity starts in an atom's nucleus, specifically when the nucleus is unstable and tries to become more stable by emitting particles such as alpha or beta particles, or energy in the form of gamma rays. This process is known as radioactive decay.
You will have an unstable carbon atom. The result will be carbon
the absorption of a free-moving neutron by the atom's nucleus
Radioactivity is caused by the instability of an atom's nucleus. An unstable nucleus can emit particles or energy in the form of radiation in order to become more stable. This process is known as radioactive decay.