The mass number of a nuclide (isotope) is simply its nucleon count: the number of protons plus the number of neutrons. In the appropriate units, it's a good approximation of the actual mass. But it's not exact. If we graph the measured "isotopic mass" of the nuclides with a given mass number, say 37, we … Continue reading Isotopic mass curves

# Category: Elements

# The half-life gap

If you sort all the nuclides (isotopes of elements) in order of increasing half life, there are a fairly steady supply of them (on a logarithmic scale) up to a half-life of about 10 million years. There are also about 250 that have a half-life so long that it has never been measured. (And for … Continue reading The half-life gap

# Bismuth became radioactive in 2003

I know this is nitpicking, but the definition of a "stable" vs. a "radioactive" isotope seems a little silly to me. The usual definition of a stable nuclide (or isotope) is one that humans have not observed to decay. A radioactive nuclide is one that humans have observed to decay. A stable element is one … Continue reading Bismuth became radioactive in 2003

# Beta-stable nuclides with the same mass number

I claimed in a previous post that, for a given atomic mass number, there is one and only one nuclide that is immune to all forms of beta decay. It occurs to me that I was probably technically wrong, especially since I made it clear that I considered atoms with different nuclear energy states to … Continue reading Beta-stable nuclides with the same mass number

# Is there any niobium-92 left?

What primordial radioactive nuclides (isotopes) still exist in the Earth's crust? To figure that out, we might need to know the original abundances of various nuclides in the matter that now makes up the Earth's crust. I haven't found good data on that. But it's pretty easy to calculate what the abundances would have to … Continue reading Is there any niobium-92 left?

# Simple classification of radioactive decay

In how many different ways can an isolated neutral non-exotic atom decay? When an atom decays, it spontaneously changes into something else. That "something else" is inevitably two or more particles, none of which is the same kind of atom as the original. I also need to also explain what a "kind of atom" is. … Continue reading Simple classification of radioactive decay