How did we develop the periodic table of elements?
Element data cards lab – build your own periodic table
Each card gives:
- mass number
- melting point, boiling point, atomic radius
- # of atoms of Oxygen and Chlorine that will combine with 1 atom of the element to make a compound.
The long form and short form of the periodic table
The most common way to arrange the elements follows this pattern
However, when you print this out on 8.5″x 11″ paper, the boxes are small and hard to read. You’d need long paper in order to make it legible. Since people prefer to read books with dimensions (aspect ratio) similar to 8.5″x 11″ they make the boxes bigger through a trick:
They cut out one section of the periodic table, and paste it below the remaining cut outs. The cuts outs are then squeezed together.
When you print that on 8.5″x 11″ paper, each box is bigger, as it uses the paper more fully.
Theoretically, the long form is more logical: In 11th grade chemistry you’ll learn about S, P, D and F electron orbitals, and how the long form of the corresponds to their arrangements. But the cut-out form is far more common.
To be clear: there are actual periods (trends) among the elements. That is real and natural, not a human convention. But how we display them on a flat piece of paper is a choice, and this choice is just a human convention. As such, one could offer different ways of grouping the elements.
The common periodic table (above) does a great job of showing many trends, but it doesn’t capture all of them. To illustrate other relationships, alternative periodic tables exist.
In this excerpt from NOVA’s “Hunting the Elements,” see how the periodic table of elements took shape…. Dmitri Mendeleev organized the elements by families with similar properties, as well as by relative weight. Find out how Mendeleev was able to predict elements that had not yet been discovered, and how the periodic table has accommodated dozens of new elements that have since been discovered.
In 1869, just five years after John Newlands put forward his law of octaves, a Russian chemist called Dmitri Mendeleev published a periodic table. Mendeleev also arranged the elements known at the time in order of relative atomic mass, but he did some other things that made his table much more successful. He realised that the physical and chemical properties of elements were related to their atomic mass in a ‘periodic’ way, and arranged them so that groups of elements with similar properties fell into vertical columns in his table.
Sometimes this method of arranging elements meant there were gaps in his horizontal rows or ‘periods’. But instead of seeing this as a problem, Mendeleev thought it simply meant that the elements which belonged in the gaps had not yet been discovered.
He was also able to work out the atomic mass of the missing elements, and so predict their properties. And when they were discovered, Mendeleev turned out to be right. For example, he predicted the properties of an undiscovered element that should fit below aluminium in his table. When this element, called gallium, was discovered in 1875, its properties were found to be close to Mendeleev’s predictions. Two other predicted elements were later discovered, lending further credit to Mendeleev’s table.
Mendeleev’s table needed one important modification before it became the modern periodic table – the use of atomic number to order the elements.
All atoms of the same element contain the same number of particles called protons, and this is called the element’s atomic number.
Mendeleev put the elements in order of their relative atomic mass, and this gave him some problems. For example, iodine has a lower relative atomic mass than tellurium, so it should come before tellurium in Mendeleev’s table. In order to get iodine in the same group as other elements with similar properties such as fluorine, chlorine and bromine, he had to put it after tellurium, so breaking his own rules.
Using atomic number instead of atomic mass as the organising principle was first proposed by the British chemist Henry Moseley in 1913, and it solved anomalies like this one. Iodine has a higher atomic number than tellurium. So, even though he didn’t know why, Mendeleev was right to place it after tellurium after all!
Element Oddities: 11 Confusing Chemical Symbols Explained
from Andy Brunning, http://www.compoundchem.com/2016/02/02/confusing-elements/
Most of the chemical symbols for elements in the periodic table make perfect sense; there are a small selection, however, that seem to bear no relation to their element’s name. After the periodic table of rejected element names a few days ago, questions about these elements came up, so here’s a look at their confusing symbols, along with the reasons behind them.
Sodium – Natrium (Na)
Sodium’s Latin name, ‘natrium’, derives from the Greek ‘nítron’ (a name for sodium carbonate). Its original source is likely to be the Arabic work ‘natrun’. A number of modern languages still call the element natrium instead of sodium, and it’s this name that its chemical symbol, Na, comes from.
Potassium – Kalium (K)
‘Kalium’ is potassium’s Latin name, and derives from the Arabic ‘al qalīy’, meaning “calcined ashes” (the ashes left over when plant material is burned). As with sodium, a number of modern languages still refer to potassium as kalium, and the name lends the element its chemical symbol, K.
Iron – Ferrum (Fe)
Iron’s Latin name, ‘ferrum’, gives it its symbol Fe; it simply means ‘iron’ or ‘sword’, and is possibly of Semitic origin. The element is known by a myriad of various names in different languages, with some sources suggesting there are over 200 different names for it. There’s a list of 213 of them here.
Copper – Cuprum (Cu)
There’s no shortage of elements named after places, but copper’s name is more subtle than most. Copper’s Latin name was ‘cyprium’, which itself comes from ‘kypros’, the Greek name for Cyprus. The island of Cyprus was famous centuries ago for its copper reserves. The name was eventually simplified to ‘cuprum’, and this eventually morphed into the English version, copper.
Silver – Argentum (Ag)
The Latin name for silver, ‘argentum’, is thought to derive originally from an Indo-European language, likely referring to the metal’s shininess. The country Argentina is named after silver (albeit indirectly as reference to the Río de la Plata) and is the only country to be named after a chemical element, rather than the other way around.
Tin – Stannum (Sn)
Tin’s Latin name, ‘stannum’, may be derived from the Indo-European ‘stag’ (dripping) because tin melts at a low temperature. There’s also speculation it could be derived from the Cornish ‘stean’ due to Cornwall’s famous tin mines, though similarly, others claim that this word is merely derived from the Latin.
Antimony – Stibium (Sb)
The Latin ‘stibium’ derives from the Greek word ‘stíbi’, meaning eye paint, referring to the use of antimony compounds as an ancient eye cosmetic. This word is in turn likely derived from Arabic or Egyptian. Few countries refer to antimony as stibium today, despite its symbol.
Tungsten – Wolfram
Wolfram was named after the mineral it was found in, wolframite. This is from the German ‘wolf rahm’, or ‘wolf’s foam’, referring to the amount of tin ‘eaten’ by the metal during its extraction. Wolfram is still used in several languages. Tungsten is from Swedish, and means heavy stone – somewhat apt, as it’s the seventh densest element in the periodic table.
Gold – Aurum (Au)
The Latin name for gold was ‘aurum’, meaning ‘yellow’, derived from the word ‘aurora’ (‘dawn’). The name ‘gold’, used in Germanic languages, means ‘yellow, shining metal’; many other European languages use derivatives of aurum.
Mercury – Hydrargyrum (Hg)
Mercury’s original Latin name was actually ‘argentum vivum’ (living silver), but Latin later borrowed from the Greek ‘hydrargyros’ (liquid silver) to give ‘hydrargyrum’. The original English name for the element was ‘quicksilver’. Alchemists considered it to be close to gold, and because of this they named it Mercury, after the planet closest to the Sun. Some of the other metals known since antiquity were given names corresponding to the planets, too, but Mercury’s is the only one that’s stuck.
Lead – Plumbum
Lead’s Latin name, ‘plumbum’, likely originally derives from a language pre-dating Ancient Greek. This Latin name is also the source of the English words ‘plumbing’ and ‘plumber’, due to the historic use of lead in water pipes.