smaller
smaller than the original atom and possibly radioactive
A proton is smaller than a nucleus, which is smaller than an atom, which is again smaller than a molecule.
They are smaller and this is why: There are less electrons to be attracted by the same original positive charge of the nucleus. (For negative ions it's just the other way around.)
The conclusion of soil erosion is that no soil remains in the original location. It has all moved into the water area, which can cause these areas to become smaller.
A cell nucleus would be smaller than a cell because a cell nucleus is inside the cell, so it has to fit inside.
An atom comprises an atomic nucleus with orbiting electrons. So the nucleus is smaller than an atom. To phrase it the opposite way, an atom is alwys larger than the nucleus (of the same atom of course!!)
because the nucleus is not an atom; an atom is smaller than a cell
"fission"
No, chromosomes are smaller than cells. Chromosomes are found in the nucleus of cells which codes for the synthesis of proteins.
Because the charge/mass ratio of a nucleus is smaller than the charge/mass ratio of an electron
A radioactive atom is an atom of an element with an unstable nucleus.
Of course, as atoms are tiny the nucleus is even smaller, but it depends on the atom. Some atoms have large protons and neutons in the nucleus, others smaller ones.