In response to Jim's question which opened this thread, and complementing some replies already posted, further details about Palladium :
en.wikipedia.org
And for comparison by those possibly interested, some details about Chromium:
en.wikipedia.org
There are presently 118 elements known to exist, and that number gets added to once in a while as a new discovery is made.
When I went to school, there were just over a hundred elements, and I was just now surprised to learn that number is now 118.
The most recently discovered elements have very short existences and are "fabricated" in nuclear accelerator research experiments.
As you'd all know, all materials are made from the elements and combinations of them.
Of the 118, perhaps only 92 are naturally-occurring, with uranium having the highest atomic number (92) of the "naturals".
But even the "92" is in dispute, with some sources saying there are actually 98 "naturals".
Each element is characterized by a so-called atomic number which is unique and equal to the number of protons in its nucleus.
In addition to the protons in the nucleus of an atom there can also be a number of neutrons, sometimes even exceeding the number of protons.
"Surrounding" the nucleus (protons + neutrons) of an atom is a "cloud" of electrons, equal in number to the number of protons.
Palladium has 46 protons and 60 neutrons, although the neutron number can vary with different "isotopes" (varieties) of palladium.
I do not have qualifications in nuclear physics, but I did get exposure to some of its fundamental concepts.
Thank you for tolerating my digression . . some may find interest . . . But, I think I have nearly reached the time limit for editing this post !
As a parting note, the precious metal element, gold, has 79 protons and 118 neutrons in its most common "natural" form.
Wikipedia is one of the Internet's fantastic resources for those wanting to explore these sorts of sidelines to pen making !
And if you dream up a good question . . . just about any question . . . fire it off to Google, as I've done many times in writing this.