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The Origins of the Periodic Table

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It's Elemental

Contrary to schoolyard rumors, no one created the periodic table just to torture you—it all started with the elements. As early as 330 BCE, Aristotle created a four-element table: earth, air, fire, and water. (We'd sign up for a test on that periodic table, no problem.) But it wasn't until the late 1700s that Antoine Lavoisier wrote the first list of 33 elements. He classified them as metals and nonmetals, though we now know that some were compounds or mixtures. Other chemists found 63 elements through the mid-1800s, including their properties and compounds, and during that time, scientists also started noticing unexpected patterns in the properties.

For example, Johann Dobereiner discovered that the atomic weight of strontium fell exactly between the weights of calcium and barium, and all three had similar properties. From this, he created the Law of Triads, which said that in triads of elements, the properties of the middle element would be the average of the other two, if you ordered the elements by atomic weight.

When other scientists tested the theory, they basically found that the triads weren't really triads but parts of larger groups. (For instance, fluorine was added to the halogen "triad.") The main drag on their research was inaccurate measuring tools—if you're trying to order the elements by weight to figure out their relationships, it would have helped to know the correct values.

Shoddy measuring tools didn't stop progress, though. Enter French geologist A.E. Beguyer de Chancourtois, who lined up the elements on a cylinder in order of increasing atomic weight. By stacking the closely related elements, he noticed that their properties repeated every seven elements. The chart had one major flaw: it included ions and compounds as well as elements. A year later (in 1864), John Newlands created the Law of Octaves. Newlands noticed the same pattern that de Chancourtois did—repetition within columns. He also arranged the elements in order of atomic weight and observed similarities between the first and ninth elements, third and eleventh, etc. Much like de Chancourtois, Newlands had one major oversight in his table: he didn't leave any spaces for elements that hadn't been discovered yet.

Symbol Minded

Five years later, we got not one, but the first two, full-fledged periodic tables. Working independently, Lothar Meyer and Dmitri Mendeleev both developed periodic tables. Meyer had published a textbook in 1864 that included an abbreviated version of a periodic table, demonstrating periodic changes in relation to atomic weight. He completed an extended table in 1868 and gave it to a colleague—who obviously took a bit too long to review it. During the review time, Mendeleev's table was published (1869), and Meyer's didn't appear until the next year.

To be fair, Mendeleev's thought process also appears to have been a little bit different than Meyer's. After noticing several patterns, he decided to create a card for each of the 63 known elements that would include the symbol, atomic weight, and chemical and physical properties. He arranged the cards on a table in order of atomic weight and grouped elements with similar properties. The table ended up showing not only group relationships, but vertical, horizontal, and diagonal relationships as well. (Alas, poor Mendeleev came only one vote away from being awarded the 1906 Nobel Prize for his work.) Unlike Meyers, Mendeleev was able to use the gaps in his table to make predictions about yet-to-be-discovered elements, and remarkably, many turned out to be true.

[See Also: Name the Noble Gases in 1 Minute]

This article was written by Liz Hunt and excerpted from the mental_floss book In the Beginning: The Origins of Everything. You can pick up a copy in our store. Also available in our store is the Periodic Table shower curtain.

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Food
New Café Geared Towards Deaf Patrons Opens in Bogotá, Colombia
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At Sin Palabras Café Sordo, a trendy new watering hole in Bogotá, Colombia, patrons can dance, play games, enjoy exhibitions and performances, and grab a drink. But while ordering from the menu, they use their hands to communicate. Sin Palabras Café Sordo—which translates to No Words Deaf Café in English—is the South American nation’s first-ever bar designed to accommodate workers and customers with hearing impairments, according to The Nation.

Located in Bogotá's Chapinero neighborhood, Sin Palabras Café Sordo has both deaf servers and menus written in sign language. Customers sit at small tables and flick on a tiny lamp to signal a bartender over to order a drink. When patrons hit the dance floor, they’re greeted by large screens playing music videos with lyrics in sign language, and a pulsing floor that allows partiers to keep in time with the beat.

A trio of Bogotá entrepreneurs—Maria Fernanda Vanegas, Cristian Melo, and Jessica Mojica—teamed up to launch Sin Palabras Café Sordo in June 2017. None of these co-owners is deaf, but Vanegas told The Nation that their goal is “for us, people who can hear, to adapt to the deaf, and not the other way round, which is always the case.” Keeping with this theme, the bar has small cards to teach non-hearing-impaired customers some basic phrases in sign language. (Visitors who don’t know enough sign language to order off the menu can point to items they want, or write them down.)

Business has been so good for Sin Palabras Café Sordo that Vanegas and her co-owners might establish even more café locations around Colombia, according to Lonely Planet. That said, they aren’t the first ones to launch a business that caters to customers with hearing impairments: Granada, Nicaragua recently became home to Café de las Sonrisas (“Smiles Cafe”), a restaurant that employs only deaf cooks and servers, and similar establishments have opened in Canada and India. And in the U.S., there are restaurants like San Francisco’s deaf-owned and -operated pizzeria, Mozzeria.

[h/t The Nation]

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Big Questions
Why Do Small Dogs Live Longer Than Large Dogs?
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Why do small dogs live longer than large dogs?

Adriana Heguy:

The issue of body size and lifespan is a fascinating topic in biology. It’s strange that across species, at least in mammals, large-bodied animals live longer than small-sized animals. For example, elephants live a lot longer than mice. The theory is that
bigger animals have slower metabolisms than small animals, and that faster metabolisms result in more accumulation of free radicals that damage tissue and DNA. But this doesn't always hold for all animals and the “rate of living” theory is not widely accepted. What we cannot clearly understand remains fascinating.

But now if we look at within a given species, lifespan and body size are inversely correlated. This is definitively the case for dogs and mice, and it has been proposed that this is the case for humans, too. Why would this be? A possible explanation is that larger dogs (or mice, or people) grow faster than their smaller counterparts because they reach a larger size in more or less the same time, and that faster growth could be correlated with higher cancer rates.

We do not have a clear understanding of why growing faster leads to accelerated aging. But it seems that it is an accelerated rate of aging, or senescence, that causes larger dogs to have shorter lifespans than little dogs.

The figure above is from Ageing: It’s a Dog’s Life. The data is from 32 breeds. Note that the inverse correlation is pretty good, however some large dog breeds, at around 40 to 50 kg (or about 88 to 110 pounds), live 12 or 13 years in average while some other dog breeds of equal body size live only eight or nine years on average. This is due to dogs being a special case, as they were artificially bred by humans to select for looks or behavior and not necessarily health, and that considerable inbreeding was necessary to produce “purebred” dogs. For example, boxers are big dogs, but their higher cancer rates may result in a shorter lifespan. However, the really giant breeds all consistently live eight to nine years on average. So there is something going on besides simple breeding quirks that led to bad genetics and ill health. Something more general.

A few years ago, a large study [PDF] was published using mortality data from thousands of dogs across 74 breeds, testing three hypotheses: Large dogs may die younger than small dogs because of (1) an earlier onset of senescence, (2) a higher minimum mortality hazard, or (3) an increased rate of aging. The conclusion from their study is that aging starts more or less at the same age in small and large breeds, but large breeds age faster. We do not have a clear understanding of the underlying mechanism for faster aging in dogs. It seems that when we selected for large body size, we selected for faster aging as well. But we do not know all the genetic components of this. We know that there are at least three genes that determine large body size in dogs: IRS4 and IGSF1, involved in thyroid hormone pathways which affect growth, and ACSL4, involved in muscle growth, and back fat thickness.

But how this accelerates aging is still speculation. More studies are needed, but dogs seem to be a great model to study the evolution of body size and its relationship to aging.

This post originally appeared on Quora. Click here to view.

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