Chemical periodic table, 150 years


Periodic table

By Elizabeth Quill, 11:29am, January 8, 2019:

150 years on, the periodic table has more stories than it has elements

Its organization holds stories of discovery and strange reactions

Recognize these rows and columns? You may remember a detail or two about this mighty table’s organization from a long-ago chemistry class. Elements are ordered according to their number of protons, or atomic number. Metals are mostly to the left and nonmetals to the right. The column at the far right holds the noble gases, named for their general unwillingness to interact with other elements.

When Dmitrii Mendeleev proposed his periodic table 150 years ago, no one knew what was inside an atom. Today, we know that an element’s place on the table, along with its chemical properties, has a lot to do with the element’s proton number as well as how its electrons are configured.

In one glance, you can see the elements that make up nature’s entire repertoire of chemical substances plus how those elements relate to one another. But the elements are also individuals, with scientific idiosyncrasies and nuanced stories of discovery. A few of our favorites are on these pages.

And the table is still a work in progress. Four elements were named as recently as 2016.  Boundary-busting research efforts, along with scientific mysteries, remain.

Potassium

Bananas are rich in potassium-40, a radioactive version of potassium. In a single banana, the potassium-40 produces a positron, the anti­matter version of the electron, a dozen or so times a day, as well as an electron about 13 times a second.

Lutetium, Lawrencium, Lanthanum, Actinium

Not everyone is convinced that lutetium and lawrencium belong in the upper positions shown here. The Royal Society of Chemistry instead puts lanthanum and actinium in these upper  boxes, prioritizing outer electron configurations and sticking lutetium and lawrencium at the end of the f-block. The International Union of Pure and Applied Chemistry, responsible for chemical naming, has been exploring the placement question since 2015.

Uranium

When Henri Becquerel, a French physicist, placed uranium salts atop photographic plates in 1896, he accidentally discovered radioactivity, for which he won the Nobel Prize in physics in 1903. Uranium is the last element on the table that occurs in any meaningful abundance in nature; the rest must be created in the lab.

Gold

Albert Einstein’s special theory of relativity explains gold’s color. Because of how electron energy levels shift due to relativity, the metal absorbs blue light, giving the reflected light a yellow hue.

Mercury

When Meriwether Lewis and William Clark set out to reach the Pacific Ocean, they carried 1,300 doses of a mercury-based laxative known as Rush’s Thunderbolts. Mercury discovered in the ground in Lolo, Mont., nearly two centuries later clued experts in to the location of one of the explorers’ campsites.

Gallium

Mendeleev left blank spaces in his original periodic table so that he could properly line up the known elements. Gallium, element 31, was his first gap to be filled, in 1875. The star of a popular chemistry trick, the metal gallium is solid at room temperature but liquid above 29.7° Celsius. It can be formed into a spoon that melts in the hand or in hot tea.

Helium 

Helium was discovered as a bright yellow line in a spectrum of light from the sun in 1868, almost three decades before the element was found on Earth. Last year, scientists reported the first sighting of helium in the atmosphere of an exoplanet.

Chlorine, Bromine, Iodine

Chlorine, bromine and iodine make up what German chemist Johann Wolfgang Döbereiner called a “triad”. Bromine’s atomic weight of 79.90 is halfway between chlorine’s (35.45) and iodine’s (126.90), and all react readily with metals to form salts. Döbereiner recognized such relationships in 1817, more than a half century before Mendeleev proposed his table.

Oganesson

Oganesson marks the end of today’s periodic table, capping the noble gases column. Yet it isn’t as aloof as others in its group. The element will readily give or take electrons, and its atoms may clump together — at least according to theoretical predictions. The few atoms of oganesson that chemists have made survived for less than a millisecond. Scientists continue smashing atoms together in the lab in search of elements beyond 118.

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Ancient organic molecules discovery on Mars


This NASA video from today in the USA says about itself:

The Curiosity rover has discovered ancient organic molecules on Mars, embedded within sedimentary rocks that are billions of years old. News Release: here.

From Chemical & Engineering News today:

Ancient organic molecules found on Mars

Curiosity rover also reports data on the red planet’s mysterious methane plumes

by Mark Peplow

Wherever life flourishes, it leaves a calling card written in organic molecules—and researchers have spent decades hoping to uncover these telltale signatures on Mars.

NASA’s Mars rover Curiosity has now given those hopes a considerable boost after finding organic deposits trapped in exposed rocks that were formed roughly 3.5 billion years ago (Science 2018). The rover’s discovery at Gale Crater shows that organic molecules were present when that part of the red planet hosted a potentially habitable lake. It also proves that these traces can survive through the ages, ready to be discovered by robot explorers.

“We started this search 40 years ago, and now we finally have a set of organic molecules that tells us this stuff is preserved near the surface,” says Jennifer L. Eigenbrode of NASA’s Goddard Space Flight Center, who led the study.

Curiosity gathered mudstone samples and gradually heated them to 860 ºC, using gas chromatography/mass spectrometry to study the gases produced. It identified a smorgasbord of molecules, including thiophene, methylthiophenes, and methanethiol, which are probably fragments from larger organic macromolecules in the sediment. These organic deposits may be something like kerogen, the fossilized organic matter found in sedimentary rocks on Earth that contains a jumble of waxy hydrocarbons and polycyclic aromatic hydrocarbons.

The organic compounds that were originally transformed into martian kerogen could have come from three possible sources—geological activity, meteorites, or living organisms—but Curiosity’s data offer no insight on that question. “The most plausible source of these organics is from outside the planet,” says Inge Loes ten Kate, an astrobiologist at Utrecht University, who was not involved in the research. She notes that roughly 100 to 300 metric tons of organic molecules arrive on Mars every year, hitching a ride on interplanetary dust particles. “Three billion years ago, it was much more hectic in the solar system”, ten Kate says, so there would have been much larger deliveries of organics via interplanetary travelers.

Curiosity had previously detected chlorocarbons in martian soil, which were probably generated by reactions with the abundant perchlorate found on the planet’s surface. In contrast, the mudstone samples have delivered “what we expect of natural organic matter,” Eigenbrode says.

Methane mystery

Meanwhile, the rover’s infrared spectrometer has been tackling the long-standing puzzle of martian methane (Science 2018). Orbiting Mars probes, along with telescopes on Earth, have previously seen occasional plumes of methane in the planet’s atmosphere, raising speculation that the gas could have come from geological activity or even methane-producing organisms.

Curiosity has taken methane measurements over 55 Earth months, spanning three martian years, which now reveal that the atmospheric concentration of the gas varies seasonally between 0.24 and 0.65 parts per billion by volume. “This is the first time that Mars methane has shown any repeatability”, says Christopher R. Webster at NASA’s Jet Propulsion Laboratory, who led the work. “It always seemed kind of random before.”

The rover also saw brief spikes in methane concentration to about 7 ppbv, which is consistent with previous remote observations of plumes, says Michael J. Mumma of NASA’s Goddard Space Flight Center, who has been chasing martian methane for more than 15 years but was not involved in Curiosity’s latest findings. “The ground-based detection is very important because it confirms the methane is there,” he says.

The methane’s source is still an open question. But Webster’s team says that the seasonal cycle rules out one of the leading suggestions: that organic molecules, delivered to the surface by meteorites and space dust, were broken down by ultraviolet light to produce the gas.

Instead, the cyclical nature of the data suggests that methane could be stored deep underground in icy crystals called clathrates and slowly escape to the planet’s topsoils. Laboratory experiments suggest that the soil could temporarily hang on to the gas, releasing more of it in the warmer martian summer to produce the seasonal cycles.

Mars’s newest satellite, the European Space Agency’s Trace Gas Orbiter (TGO), could help confirm that idea. It began to survey the whole planet for methane in April. “We’re all waiting with bated breath to see what they find,” Webster says. TGO should also measure the carbon isotope ratios in the methane it detects, which may provide hints at a biological or geological origin. And in 2021, ESA expects to land a rover on Mars that could drill up to 2 meters below the surface, where there might be better-preserved organics compared with the ones collected at Gale Crater, Eigenbrode says.

These lines of evidence could eventually help resolve questions about our own origins. Mars and Earth were once quite similar places, ten Kate says, yet life apparently failed to gain a foothold on the red planet. “Was there really no life on Mars, or did it just not survive?” she says. The answer could shed light on the crucial conditions needed to nurture the first life-forms on our own world.

See also here.

Opportunity rover waits out a huge dust storm on Mars. The 14-year-old craft has weathered storms before, but none this big, by Lisa Grossman, 5:56pm, June 11, 2018.

A team of astronomers using data collected from the Mars Express spacecraft have published 29 low-frequency radar images collected between May 2012 and December 2015. Taken together, they reveal a change in the structure and the composition of the material beneath the surface of Mars’ south pole that so far has only one explanation: the presence of liquid water under the surface of the red planet. This is a milestone in the 54 years of Mars space exploration: here.

London Grenfell disaster survivor girl gets top school grades


This TV video from Britain says about itself:

16 June 2017

16-year-old Ines Alves and her brother Tiago lived on the 13th floor of Grenfell Tower. They both ended up running for lives on the night of the fire, but the very next morning, Ines went back to school to sit her chemistry GCSE exam. They share their story.

By Felicity Collier in London, England:

Grenfell: Survivor who sat exam hours after fire gets top grades

Friday 25th August 2017

A TEENAGER who escaped from Grenfell Tower and sat her chemistry GCSE the next morning was awarded an A grade yesterday.

Ines Alves, who lived with her family on the 13th floor, fled the fire in the middle of the night with just her mobile phone and chemistry notes before sitting the exam at 9am still wearing the same clothes.

The 16-year-old also scored the highest possible grades in maths — a 9 which is equivalent to an A* under the old system — and A* in Spanish.

Sacred Heart High School head teacher Marian Doyle called her results “fantastic.”

“It must have been so hard for her to actually come in and do that and try to blot out the scenes of what she had seen,” she said.

The student said that at first she thought the fire was “nothing major” and had just wanted to sit the paper, adding: “There was no point me carrying on watching the building burning so I just went in.”

Asked what she remembered from the night, she said: “The whole thing. The screaming, people screaming, begging for help.”

More than two months on Ms Alves’s family — who owned the flat — are living in a hotel and are still waiting until they are offered a permanent home.

‘Oxygen on comet 67P not that ancient’


This 8 May 2017 video is called Study Suggests Alternative For Oxygen Formation On Comets.

From Science News:

Oxygen on comet 67P might not be ancient after all

Newly discovered chemical reaction could generate the gas instead, study suggests

By Ashley Yeager

12:28pm, May 8, 2017

Oxygen on comets might not date all the way back to the birth of the solar system.

Instead, interactions between water, particles streaming from the sun and grains of sand or rust on the comet’s surface could generate the gas. Those interactions could explain the surprising abundance of O2 detected in the fuzzy envelope of gas around comet 67P/Churyumov-Gerasimenko in 2015 (SN: 11/28/15, p. 6), researchers report May 8 in Nature Communications. Such reactions might also reveal how oxygen forms in other regions of space.

Molecular oxygen is very hard to find out there in the universe,” says Caltech chemical engineer Konstantinos Giapis. When the Rosetta spacecraft detected oxygen around comet 67P, astronomers argued it must be primordial, trapped in water ice as the comet formed roughly 4.6 billion years ago. Intrigued by the result, Giapis and Caltech colleague Yunxi Yao wanted to see if an alternative way to create O2 existed. Drawing on their work with fast-moving charged particles and materials such as silicon, they performed experiments that showed that charged water particles could slam into rust or sand grains and generate O2.

Something similar could happen on comet 67P, they suggest. As the sun evaporates water from the comet’s surface, ultraviolet light could strip an electron from the water, giving it a positive charge. Then, fast-moving particles in the solar wind could shoot the ionized water back toward the comet’s surface, where it could collide with rust or sand particles. Atoms of oxygen from the water could pair with atoms of oxygen from the rust or sand, creating O2.

The idea is plausible, says Paul Goldsmith, an astrophysicist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. He helped discover O2 in the Orion nebula and says the reaction might happen in places where young stars are forming and in other regions of space.

Rosetta mission scientist Kathrin Altwegg of the University of Bern in Switzerland calls the result interesting, but is skeptical it can explain comet 67P’s oxygen abundance. As the comet gets closer to the sun, a protective bubble develops around 67P, data from the mission showed; that bubble would prevent solar wind particles or other ionized particles from reaching the comet’s surface, Altwegg says. Also, the ratio of oxygen to un-ionized water also stays constant over time. It should be more variable if this chemical reaction were generating oxygen on the comet, she says.

Goldsmith, however, suggests researchers keep an open mind and design missions with instruments to test whether this newly detected reaction does, in fact, generate oxygen in space.

See a new mosaic of images of comet 67P from the Rosetta mission: here.

The cigar-shaped object called ‘Oumuamua spotted tumbling through space last year is a comet, scientists have confirmed. ‘Oumuamua was the first interstellar object found passing through our solar system.

Gold, new chemical discoveries


This video says about itself:

18 July 2012

In this video we explore the chemical resistance of gold.

The gold coin survives hydrochloric acid, nitric acid, sulfuric acid, bleach (sodium hypochlorite) and sodium hydroxide

From Science News:

Chemists strike gold, solve mystery about precious metal’s properties

Predicted, actual energy needed for ionization now match

By Emily Conover

7:00am, January 23, 2017

Gold’s glimmer is not the only reason the element is so captivating. For decades, scientists have puzzled over why theoretical predictions of gold’s properties don’t match up with experiments. Now, highly detailed calculations have erased the discrepancy, according to a paper published in the Jan. 13 Physical Review Letters.

At issue was the energy required to remove an electron from a gold atom, or ionize it. Theoretical calculations of this ionization energy differed from scientists’ measurements. Likewise, the energy released when adding an electron — a quantity known as the electron affinity — was also off the mark. How easily an atom gives up or accepts electrons is important for understanding how elements react with other substances.

“It was well known that gold is a difficult system,” says chemist Sourav Pal of the Indian Institute of Technology Bombay, who was not involved with the study. Even gold’s most obvious feature can’t be explained without calling Einstein’s special theory of relativity into play: The theory accounts for gold’s yellowish color. (Special relativity shifts around the energy levels of electrons in gold atoms, causing the metal to absorb blue light, and thereby making reflected light appear more yellow).

With this new study, scientists have finally resolved the lingering questions about the energy involved in removing or adding an electron to the atom. “That is the main significance of this paper,” Pal says.

Early calculations, performed in the 1990s, differed from the predicted energies by more than a percent, and improved calculations since then still didn’t match the measured value. “Every time I went to a conference, people discussed that and asked, ‘What the hell is going on?’” says study coauthor Peter Schwerdtfeger, a chemist at Massey University Auckland in New Zealand.

The solution required a more complete consideration of the complex interplay among gold’s 79 electrons. Using advanced supercomputers to calculate the interactions of up to five of gold’s electrons at a time, the scientists resolved the discrepancy. Previous calculations had considered up to three electrons at a time. Also essential to include in the calculation were the effects of special relativity and the theory of quantum electrodynamics, which describes the quantum physics of particles like electrons.

The result indicates that gold indeed adheres to expectations — when calculations are detailed enough. “Quantum theory works perfectly well, and that makes me extremely happy,” says Schwerdtfeger.

Smashing gold ions creates most swirly fluid ever. Record-making vorticity found in quark-gluon plasma. By Emily Conover, 12:00pm, February 8, 2017: here.

Four new elements in periodic table


The periodic table’s newest elements now have names. The International Union of Pure and Applied Chemistry approved the names nihonium (Nh), moscovium (Mc), tennessine (Ts) and oganesson (Og) on November 28

From Science News:

Names for four new elements get seal of approval

Countless periodic table posters are now obsolete

by Emily Conover

1:35pm, November 30, 2016

Meet the newest elements: nihonium (Nh), moscovium (Mc), tennessine (Ts) and oganesson (Og). On November 28, the International Union of Pure and Applied Chemistry gave their seal of approval to the names proposed for the four elements, which take slots 113, 115, 117 and 118 on the periodic table.

The new names, proposed in June, underwent five months of public comment and review. IUPAC decided to let the names stand, and unwieldy placeholder names — ununtrium, ununpentium, ununseptium and ununoctium — assigned when the elements were added to the periodic table in December 2015, can now be scrubbed.

Three of the elements were named for the places they were discovered. The name of element 113, “nihonium,” comes from the word “Nihon,” a Japanese word for the country of Japan. Element 115 is dubbed “moscovium,” after Moscow. And element 117, tennessine, is named after Tennessee. Element 118, oganesson, honors physicist Yuri Oganessian.

Scientists have produced a new form of hydrogen in the lab — negatively charged hydrogen clusters: here.

Moon rocks, asteroid impacts miscalculation?


This video says about itself:

Astronomy – Ch. 8: Origin of the Solar System (16 of 19) Late Heavy Bombardment

21 March 2015

In this video I will explain how astronomers deduced that early Solar System was a very violent place.

The video shows most scientists’ views of a year ago.

However, now …

From Science News:

Moon rocks may have misled asteroid bombardment dating

Spike in impacts 3.9 billion years ago may be mathematical mirage, study finds

By Laurel Hamers

3:00pm, September 12, 2016

A barrage of rocks hitting the solar system 3.9 billion years ago could have dramatically reshaped Earth’s geology and atmosphere. But some of the evidence for this proposed bombardment might be shakier than previously believed, new research suggests. Simplifications made when dating moon rocks could make it appear that asteroid and comet impacts spiked around this time even if the collision rate was actually decreasing, scientists report the week of September 12 in the Proceedings of the National Academies of Sciences.

Many scientists think that a period of relative calm after Earth formed 4.6 billion years ago was interrupted by a period called the Late Heavy Bombardment, when rocky debris pummeled Earth and the other planets. The moon’s cratered surface holds the best evidence for this event; scientists have measured radioactive decay of argon gas trapped inside moon rocks to date when craters on the moon were formed.

Many of the hundreds of moon rocks analyzed appear to be around 3.9 billion years old. That suggests the number of rocks hitting the moon suddenly spiked at that time — evidence for a Late Heavy Bombardment.

Geochemists Patrick Boehnke and Mark Harrison of UCLA took a second look at the data. Measuring argon from the same rock at different temperatures leeches the gas from different parts of the rock’s crystals; if all those age values align, researchers can be relatively confident they’re getting an accurate age. But many of the lunar samples previously analyzed gave different ages depending on the temperature at which their argon content was measured.

Instead of colliding sharply once and sitting undisrupted, which might give more uniform age data at different temperatures, these lunar rocks were probably tossed around and slammed into other rocks many times, Boehnke says. So assigning one impact age to those rocks might be an oversimplification.

Boehnke and Harrison created a model to simulate how this simplification might affect the patterns seen when scientists looked at the ages of many rocks. The team modeled 1,000 rocks and assigned each one an impact age. Some rocks hadn’t been knocked around and had a clear impact age. Others had been smashed repeatedly, which changed their argon content and obscured the actual impact age assigned by the model.

The model assumed that asteroid collisions decreased over time — that more of the rocks were older and fewer were newer. But still, collision ages appeared to spike 3.9 billion years ago thanks to the fuzziness introduced by the disrupted rocks. So the apparent asteroid increase at that time might just be a quirk due to the way the argon dating data were compiled and analyzed, not an indication of something dramatic actually happening.

“We can’t say the Late Heavy Bombardment didn’t happen,” Boehnke says. Nor do the results invalidate the technique of argon dating, which is used widely by geologists. Instead, Boehnke says, it points to the need for more nuanced interpretation of lunar rock data.

“A lot of data that shows this complexity is being interpreted in a very simplistic way,” he says.

Planetary scientist Simone Marchi says he finds the paper “certainly convincing in saying that we have to be very careful” when interpreting argon dating data from lunar samples.

But there’s other evidence for a Late Heavy Bombardment that doesn’t rely on argon dating, such as dating from more stable radioactive elements and analysis of overlapping craters on the moon, says Marchi, of the Southwest Research Institute in Boulder, Colo. He supports the idea of a gentler Late Heavy Bombardment 4.1 billion years ago, instead of a dramatic burst 3.9 billion years ago (SN: 8/23/14, p.13).

Other recent work has also pointed out limitations in argon dating, says Noah Petro, a planetary geologist at NASA Goddard Space Flight Center in Greenbelt, Md., who wasn’t part of the study.   Collecting new samples and analyzing old ones with newer techniques could help scientists update their view of the early solar system. “We’re at this point with the moon right now where we’re finding the limitations of what we think we know.”

See also here.

Where the young hot Earth cached its gold. New view offers alternative history of how precious metals sank into the planet’s core: here.

A team of scientists has determined the number of asteroid impacts on the Moon and Earth increased by two to three times starting around 290 million years ago. Previous theories held that there were fewer craters on both objects dating back to before that time because they had disappeared due to erosion. The new findings claim that there were simply fewer asteroid impacts during that earlier period: here.