OPEN THREAD 20200217

Basically, all legal free speech is allowed. We will assist the authorities in dealing with illegal speech. You are each other’s moderators. Have fun. And don’t forget to MAGA at nuclear levels.

Citizen U

Day 103 – LAWRENCIUM.

20 thoughts on “OPEN THREAD 20200217

    1. One of the things about the current construct of the periodic table is that it nicely segregates the lanthanides and actinides in terms of populating f orbitals. Problem is, when you get to orbitals farther from the nucleus, they don’t always populate Ns, Np, Nd, and Nf in an organized fashion. For example, the predicted orbitals for Lr would be [Rn]5f14,6d1,7s2, while it is likely they actually are [Rn]5f14,7s2,7p1 .

      For the not-too-technical read on this — Lr would rather put an electron on a p shell 7 away from the nucleus than put it on a d shell 6 away from the nucleus. One could ascribe this to a number of factors, including my favorite — “relativistic effects” — but let’s just put it down to plain cussedness for the moment.

      This is a valence electron — used for chemical reactions. putting it farther from the nucleus means that it’d be easier for Lr to give up…..where an electron on a closer-in d shell would make Lr less likely to give it up.

      When you’re trying to bring order out of chaos, it’s best to stick with simple rules and remember exceptions instead of building exceptions into rules.

      Liked by 3 people

      1. There are plenty of elements well down into the stable range that don’t do as expected, palladium sticks out like a sore thumb in that regard.

        The table is pretty much laid out to follow the Aufbau principle (https://en.wikipedia.org/wiki/Aufbau_principle) regardless of what the elements actually do.

        Though if we follow Aufbau, then we must put scandium and yttrium above lutetium and lawrencium, not above lanthanum and actinium.

        Liked by 2 people

  1. Lawrencium is named after Ernest Lawrence, inventor of the cyclotron. Ironically, the cyclotron that had been so fruitful for the Berkeley research team could not be used after the discovery of mendelevium, because substantially more massive particles needed to be accelerated — the HILAC accelerator was used, instead. So an element that illustrated the limitations of cyclotrons was named after the inventor of the cyclotron.

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  2. There are two isotopes of lawrencium of any importance, 260, with a half life of 2.7 minutes. and 266 with a half life of 11 hours (wow, it beats astatine and francium!)

    260 is much easier to produce, so when they want to try to experiment with lawrencium chemistry, it’s done with Lr-260.

    On doing so they find it’s very similar to lutetium, the element above it in the table, and that’s to be expected.

    Lr-260 and Lr=256 are generally produced by bombarding americium, curium, berkelium, californium or einsteinium with boron, carbon, nitrogen, oxygen, fluorine or neon nuclei. In particular, Lr-256 (half life 27 seconds) comes from Ca-249+B-11 (four spare neutrons), and Lr-260 comes from Bk-249 with O-18, with an alpha particle and three neutrons as spare pieces.

    The known isotopes span from Lr-251-262, and 266. Thus there’s a gap, containing 263-265; and the expectation is these would have 5-10 hour half lives. Note that the heaviest isotope is by far the most stable of the bunch. This is going to be a notable trend.

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  3. Consider hydrogen. 1 proton, zero neutrons is a perfectly stable isotope. Helium, 1 neutron, two protons is stable (though 2 and 2 is rock solid stable, more so than He-3). You can do a quick division; H-1 has a neutron ratio of 0, He-3 has a neutron ratio or 1.

    Past this point you need as many neutrons as protons, at least, for stability–a neutron ratio of 1 or more. Calcium can get by with a fifty fifty mix, 20 neutrons, 20 protons. But the very next element requires 24 neutrons to hold its 21 protons together. That’s a neutron ratio of 1.14+.

    I haven’t done an exhaustive look but I don’t think any element after calcium has a stable isotope with a neutron ratio of 1.0.

    So there’s clearly a trend of requiring higher and higher neutron ratios.

    Lead 204, 206, 207 and 208 are all stable. Note that lead has 82 protons, so the isotopes have 122, 124, 125, and 126 neutrons. Basically, the neutron ratio is about 1.5 (lead 205 would have a perfect 1.5 ratio).

    Uranium is worse…it has ten neutrons more than lead, yet the isotopes are THIRTY numbers higher; it needs, basically, two more neutrons per additional proton just to be almost stable.

    From this point forward, to get the most stable isotope, you should add two neutrons for each proton.

    But if we’re going to go bombarding big atoms with smaller (but still significant) atoms to try to get past fermium, we’ve got a problem. Those smaller atoms don’t contain nearly enough neutrons to give us the most stable isotope of the new element. It’s even worse when the new nucleus sheds three or four neutrons as it’s made!

    I pointed out before that Lawrencium’s most stable isotope is Lr-266, and that that is the heaviest isotope known so far. That just about screams the question of what we could do if only we could add more neutrons to it. Could we gin something up with a half life of years?

    Calcium has a stable isotope, Ca-48, which has an unusually high number of neutrons for its size (eight more than the 1.0 ratio would call for), so it’s often used to try to create heavy elements, but even it doesn’t bring enough to the table.

    Each of these elements, from here on out has a band of possible isotopes which we can take an educated guess at. If the isotope number is too low, the nucleus will simply shed protons; that’s the “proton drip line.” If the number is too high, the isotope simply sheds neutrons, that’s the neutron drip line.

    As we proceed beyond lawrencium, we get closer and closer to the proton drip line, which is why it’s hard to make additional progress past where we are right now (118, oganesson). We’re just barely this side of the proton drip line there, and we can’t find a nucleus with enough spare neutrons in it to bombard with, to try to make element 119.

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  4. There has been a lot of speculation that there might be an “island of stability” around element 114, or even a higher number. Isotopes with significantly longer half lives might exist. Some people even have a wet dream that there could be a stable isotope or two out there. Imagine, for instance, super dense but stable metals below lead…

    But we simply can’t throw enough neutrons at these guys to get them further away from the proton drip line. Interestingly, when we make a very heavy nucleus like 114, sometimes in its decay chain we will see heavier nuclei of things like 110, 108, and 106 than we can get directly. This is because the usual decay mode is alpha particles, and because they remove two protons and two neutrons, they leave something behind that’s a lower element number AND a higher neutron ratio. And those new isotopes often have much higher half lives than anything we could make directly.

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      1. The most stable line through the table of isotopes has, on the one side, alpha decay to bring the neutron ratio up, by shedding, proportionately, more protons, and on the other side, you have beta decay to swing the balance back towards protons (by turning a neutron into a proton).

        This is why, after U-238 kicks out an alpha particle to become Th-234…Th-234 undergoes beta decay. It has too many neutrons to be the most stable thorium isotope. So eventually it becomes U-234, which then decays to Th-230, which now doesn’t have enough neutrons (Th-232 has the right number), so an alpha decay is called for. I don’t even have to look at the table to see that. (I did, though, just check, and I was right.) We seesaw back and forth across that “most stable” line until we hit a lead isotope which IS stable.

        Elements from here on out have WAY too few neutrons after we do the bombardment, so they decay via alpha decay, rep[eatedly. The result is we get some lighter (but still very heavy elements) with better neutron ratios than we get when we create those elements directly.

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  5. Believe it or not, I had a complete audio score worked up yesterday before Marica came by and I switched it to early Beatles…..and now I’m sitting here going d’uh…..

    Let’s go this way —

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  6. Vacationing in Hawaii, two priests decide to wear casual clothes so they won’t be identified as clergy.
    They buy Hawaiian shirts and sandals, and soon hit the beach. They notice a gorgeous blonde in a tiny bikini.

    “Good afternoon, Fathers,” she says as she strolls by.

    The men are stunned. How does she know they’re clergy? Later they buy even wilder attire: surfer shorts, tie-dyed T-shirts, and dark glasses.

    The next day, they return to the beach. The same fabulous blonde, now wearing a string bikini, passes by, nods politely at them, and says, “Good morning, Fathers.”

    “Just a minute, young lady,” says one of the priests. “We are priests and proud of it, but how in the world did you know?”

    “Don’t you recognize me? I’m Sister Kathryn from the convent.”

    Liked by 1 person

  7. A man who has been stranded on a deserted island all alone for 10 years sees a speck on the horizon. “It’s too small to be a ship,” he thinks to himself. As the speck gets closer, he rules out the possibility of it being a small boat, then a raft.

    Suddenly, a gorgeous blonde woman emerges from the surf wearing a wet suit and scuba gear. She approaches the stunned man and asks, “How long has it been since you’ve had a cigarette?”

    “Ten years!” he says.

    She unzips a waterproof pocket on her left sleeve and pulls out a pack of fresh cigarettes. He takes one, lights it, takes a long drag, and says, “Man, is that ever good!”

    Then she asks him, “How long has it been since you’ve had a sip of bourbon?”

    Trembling, he replies, “Ten years!”

    She unzips a waterproof pocket on her right sleeve, pulls out a flask, and gives it to him. He opens it, takes a long swig, and says, “That’s fantastic!”

    Then she starts slowly unzipping the long zipper down the front of her suit, looks at him seductively, and asks, “And how long has it been since you’ve played around?”

    The man, with tears in his eyes, replies, “Don’t tell me you’ve got golf clubs in there!

    Liked by 1 person

  8. A Californian surfer visiting Australia was having a good time catching the breakers at resorts along the Gold Coast, but wanted a special experience. He wanted to surf a beach where nobody, or almost nobody, goes.

    So he gets in the car, drives north. At the first remote beach he hits, he has his board in hand as he’s walking toward the water, when one of the locals warns him: “you don’t want to be surfing here, mate: there’s too many sharks”.

    So he heeds the warning, and drives to one remote beach after another – and it’s always the same warning: there’s too many sharks.

    Finally, he finds a perfect beach. It’s so perfect, film editors would cut it out because the audience would never believe it’s real. He asks the first person he meets if there are any sharks here, and was told, no.

    Two more locals give him the same answer: no sharks here. So he splashes into the water and paddles out toward the breakers, when the alarm goes off in his head. This is a perfect beach, the water temperature’s perfect, the breakers are to die for… and not only are there no surfers, nobody is in the water. Something’s got to be wrong.

    So he turns his head and cries out to a sunbather catching a tan: “Hey, why aren’t there any sharks at this beach?”

    And the guy answers: “because they’re bloody afraid of the crocodiles, mate!”

    Liked by 1 person

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