Answer to this is Radioactive isotopes.
Isotopes are the species of the same element having different atomic masses that means the number of protons remains the same but number of neutrons do differ. For example 
and 
are the two isotopes of Hydrogen (
).
Radioactive isotopes are the isotopes which release some kind of energy in the form of alpha particles, beta particles or gamma radiation. Examples of each of the decay processes are :
Alpha Decay: In this decay one alpha particle having atomic mass 4 and atomic number 2 or we can say a He molecule will come out. 
Beta Decay: In this decay a 
particle is emitted increasing the atomic number of the reactant by 1 unit.
Gamma Radiation: In this type of reaction only radiation is emitted out which does not change the original molecule.
Simply put, Potential energy is the "build up". If I had a ball on the top a 5ft slide, it would have potential energy, as long as it hasn't slid down yet.
If I had another ball on a 10ft slide, it would have twice the potential energy the first ball had.
What comes next is kinetic energy, which is the energy used when the object is moving, like the ball as it goes down the slide. The faster it moves, the more kinetic energy.
Basically, <em>Potential</em> is the "build up" but it does not, I repeat does not move.
<em>Kinetic</em> energy is the use of the "build up" through movement.
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<u>ANSWER</u></h3>
2. Neon, only
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<u>EXPLANATION</u></h3>
When Na and F combine they form an electron configuration of 2-8. Na electron configuration is 2-8-1 while F is 2-7, so when they form an ionic bond F will gain Na outermost electron to complete its valence shell due to having a higher negativity. Neon has an electron configuration of 2-8 but argon has 2-8-8.
Explanation:
Derived quantities are quantities that are calculated from two or more measurements. They include area, volume, and density. The area of a rectangular surface is calculated as its length multiplied by its width. The volume of a rectangular solid is calculated as the product of its length, width, and height.
Actually, there are only about 100 atoms that have been yet discovered. But each element has many different kinds of atom. For instance, carbon. Do you know carbon has more than 30 or 50 different types of atoms? Well, how? There are isotopes. Don't think that there is only one carbon atom which has 6 electrons and 6 protons and 6 neutrons. There are more. C-13 has 6 electrons and 6 protons and 7 neutrons. While, C-14 has 6 electrons and 6 protons and 8 neutrons. I just showed you three stable isotopes of carbon(element). But, what is really an isotope?? Did you notice that all of these atoms had the same number of protons and electron but different numbers of neutrons? This is really an isotope. Well, if an atom takes a few more electrons or gives off a few electrons, it still stays the same element/ atom type. Just like that an element can have atoms of different neutron number. It may be less or more. It doesn't affect the atom much: just makes an isotope. But it does affect the atomic mass number or radioactivity of an atom. So, an element can have many different forms of isotopes of its atoms. In this way, being only 100 atoms, there can 1000 atoms or (more than that!).
To make it more clear-
Definition of ISOTOPE: <span>any of two or more forms of a </span>chemical<span> element, having the same number of protons and electrons in the nucleus, or the same atomic number, but having different numbers of neutrons</span>
HOPE YOU UNDERSTOOD THE MATTER:-))
