Plumped up carbon fatter than expected

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Check the periodic table you have hanging on your wall—I know I'm not the only one who has one—and you'll see a weight for each element. This is the element's accepted atomic weight, but it only represents a weighted average of the masses of all the isotopes present in nature. Past experimental research has shown that a pretty consistent trend exists: the size of an atom's nucleus correlates with its mass number (the total number of neutrons and protons in the nucleus). Generally, the size of the nucleus is proportional to the cube root of the mass number.

Every now and then, however, we find an isotope where this relationship does not hold. Recently, it was discovered that 22C (Carbon-22, a carbon atom with six protons and 16 neutrons instead of the normal six and six) has a nucleus that is bigger than 208Pb! Going by the cube root rule of thumb, one would expect it to only be about 20 percent larger than 12C. The reason for this, according to a paper in an upcoming edition of Physical Review Letters, is that 22C represents the largest known "halo" nucleus to date.

Rest of the story: ... pected.ars


What do they mean when it says in the story "These neutrons have a significant probability of tunneling beyond the area in which the nucleus is normally confined."?

By using the word "tunneling" I get the feeling there is something outside of the nucleus. Or, do they mean punching through the nucleus and if that's the case what is the nucleus membrane made of?

LOL sorry to bug you but hey you piqued my interest.
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