Group items tagged

silver as an example

has the same number of protons

Silver has 47

not every atom of an element necessarily has the same number of neutrons

different versions of an element's atoms are called isotopes

Silver occurs as silver-109 and silver-107

Chemists calculate the atomic weight of an element that you see on the periodic table from the masses of its isotopes, giving more common isotopes more weight than less common isotopes

doesn't necessarily mean every sample of silver on Earth has an atomic weight of exactly

samples of elements vary from place to place

erences play an important role in many sciences

They help chemists trace the origin of different materials

and date archaeological findings

The latest atomic weights measurements differ too little from their predecessors to really change science

do it?"

If it's just small changes, why

should give the best numbers there are

some new idea will come up that needs more accurate data

Molybdenum, Losing 0.0122

Atomic weights are relative, so they don't have units

Thorium, Losing 0.000322

Yttrium and Niobium, Tied, Losing 0.00001

Selenium, Gaining 0.0088

Cadmium, Gaining 0.0026

Holmium, Thulium and Praseodymium, All Tied, Gaining 0.00001

The changes in weights mostly come from continuing improvements in atomic mass measurements

advances in the technology behind mass spectrometers

not all about measuring more accurately

thorium, the IUPAC decided to recognize an isotope, thorium-230, that it previously thought was too rare to include in atomic weight calculations

The last time international chemistry

really altered the periodic table was in 2009, when IUPAC decided to list the atomic weights of some elements as ranges, instead of single numbers

markings suggest dates thousands of years in the future

Perhaps most important, the otherwise humble chamber offers a rare glimpse into the inner workings of Maya society

in today's Xultún

just 6 square miles (16 square kilometers) of jungle floor—it's a wonder Saturno's team found the artwork at all

At the Guatemalan site in 2010 the Boston University archaeologist and Ph.D. student Franco Rossi were inspecting a looters' tunnel, where an undergraduate student had noticed the faintest traces of paint on a thin stucco wall.

began cleaning off 1,200-year-old mud and suddenly a little more red paint appeared.

What the team found, after a full excavation in 2011, is likely the ancient workroom of a Maya scribe, a record-keeper of Xultún.

this was a workspace. People were seated on this bench" painting books that have long since disintegrated

The books would have been filled with elaborate calculations intended to predict the city's fortunes. The numbers on the wall were "fixed tabulations that they can then refer to—tables more or less like those in the back of your chemistry book," he added.

Undoubtedly this type of room exists at every Maya site in the Late Classic [period] and probably earlier, but it's our only example thus far."

Maya civilization spanned much of what are now Guatemala, Belize, and Mexico's Yucatán region. Around A.D. 900 the Classic Maya centers, including Xultún, collapsed after a series of droughts and perhaps political conflicts

The apparent desperation of those final years may have played out on the walls of the newly revealed room—the only major excavation so far in Xultún.

Despite past looting, the interior of the newfound room is nearly perfectly preserved.

Among the artworks on the three intact walls is a detailed orange painting of a man wearing white disks on his head and chest—likely the scribe himself

the researchers noticed several barely visible hieroglyphic texts, painted and etched along the east and north walls of the room

One is a lunar table, and the other is a "ring number"—something previously known only from much later Maya books, where it was used as part of a backward calculation in establishing a base date for planetary cycles

Nearby is a sequence of numbered intervals corresponding to key calendrical and planetary cycles.

The calculations include dates some 7,000 years in the future

The Maya at Xultún were likely less concerned with the end of the world than the end of their world

Sadly, we may never understand the full context of the workroom. Many of the glyphs are badly faded. Worse, the entire city of Xultún was looted clean during the 70s, leaving very little other writing or antiquities.

Because of this, and despite Xultún's obvious prominence in the Maya world, many archaeologists had written off the

Curiosity has protections against such high-energy disruptions, but the problem was compounded by what appears to have been the location of the strike—in the directory, or "table of contents," of the computer's memory

appears to have caused the computer to get stuck in an endless loop.

previous rovers experienced many so-called "anomalies" during the early part of their treks

Even if the rover is fully operational again in a week, the amount of science it can perform is limited.

the sun comes between Mars and the Earth in early April, partially blocking the path for radio commands for an entire month

The Curiosity team had planned to send back science data from Mars during that period—called "solar conjunction"—but had decided not to send up any commands.

flakes are soluble in liquids and easily produced in bulk

The discovery

could be a boon in the cleanup of contaminated sites like the Fukushima nuclear plants

could also cut the cost of hydraulic fracturing ("fracking") for oil and gas recovery and help reboot American mining of rare earth metals

Graphene oxide's large surface area defines its capacity to adsorb toxins

high retention properties are not surprising

What is astonishing is the very fast kinetics of sorption, which is key

the collaboration took root when

a graduate student

graduate student in Kalmykov's group, met at a conference several years ago.

researchers focused on removing radioactive isotopes of the actinides and lanthanides – the 30 rare earth elements in the periodic table – from liquids, rather than solids or gases

Naturally occurring radionuclides are also unwelcome in fracking fluids that bring them to the surface in drilling operations

When groundwater comes out of a well and it's radioactive above a certain level, they can't put it back into the ground

Companies have to ship contaminated water to repository sites around the country at very large expense

The ability to quickly filter out contaminants on-site would save a great deal of money

even greater potential benefits for the mining industry

Environmental requirements have "essentially shut down U.S. mining of rare earth metals, which are needed for cell phones

China owns the market because they're not subject to the same environmental standards

this technology offers the chance to revive mining here, it could be huge

capturing radionuclides does not make them less radioactive, just easier to handle

Where you have huge pools of radioactive material, like at Fukushima, you add graphene oxide and get back a solid material from what were just ions in a solution

Then you can skim it off and burn it

Graphene oxide burns very rapidly and leaves a cake of radioactive material you can then reuse

The low cost and biodegradable qualities of graphene oxide should make it appropriate for use in permeable reactive barriers, a fairly new technology for in situ groundwater remediation,

Super-heavy elements do not occur in nature and have to be discovered in the lab, using particle accelerators, nuclear reactors, ion separators and other complex equipment

Science have been hunting for 113 for nine years, and have claimed to see it a few times already — but the evidence has never been this clear,

the team used a customized gas-filled recoil ion separator paired with a semiconductor detector that can pick out atomic reaction products

created element 113 by speeding zinc ions through a linear accelerator until they reached 10 percent of the speed of light.

ions then smashed into a piece of bismuth. When the zinc and bismuth atoms fused, they produced an atom with 113 protons