Periodic Table

The Periodic Table is a chart which organises chemical elements into groups based on their various properties — ascending by atomic number and grouped by things such as reactivity and valency. While it was first organised by these macroscopic properties, it actually forms a map of the atomic orbital structure indicating how quantum mechanical concepts relate to chemical properties. The most commonly accepted version of the Periodic Table was invented by Russian chemist Dmitri Mendeleyev in the second half of the 19th century, though others were part of a push towards order in the chemical worldhttps://www.asbmb.org/asbmb-today/science/020721/a-brief-history-of-the-periodic-table.
==Origins==
Chemical behaviour is generally very messy, complicated, and irregular.More specifically:
*Inorganic Chemist: "Inorganic chemistry is messy, complicated and irregular and therefore interesting. Organic chemistry is boring and predictable." 
*Organic Chemist: "Organic chemistry is messy, complicated and irregular and therefore interesting. Inorganic chemistry is boring and predictable." Chemists, in contrast, enjoy making neat and tidy lists of things. By the 17th century, chemists had begun to use the concept of an "element" in its modern sense (i.e. a substance which cannot be broken down into a simpler substance using chemical means) — which was nice and tidy — but, distressingly, they had also begun to discover dozens of new elements besides those which had been known for centuries — this was distressingly untidy. A glimmer of hope was at hand, however: it was noticed that many of these newly discovered elements appeared to exhibit similar properties, seeming almost to belong to 'families'. Moreover, these similar properties often seemed to exhibit trends when the elements were placed in order of . Examples included "triads" such as chlorine, bromine, and iodine, and copper, silver, and gold.
The race was on amongst chemists to draw up some kind of nice tidy list which would arrange the ever-increasing numbers of these pesky new elements in some kind of elegant way which brought order to the increasing chemical mess. The breakthrough was finally made by Mendeleev. His Table managed to set out the elements in rows and columns, in order (more or less) of atomic weight, so that those elements with similar properties fell into nice tidy vertical groups. Mendeleev made two particular innovations over previous pedants:
*in a couple of cases where listing the elements in order of atomic weight would have messed up his groups, he swapped elements around so that they fitted the pattern
*in further cases where listing the elements in any order wouldn't fit the pattern at all, he declared there must be a "missing element" and left a gap for it in the table.
However, Mendeleev couldn't, at the time, provide any physical explanation of why there should be missing elements, or why atomic weights occasionally needed swapping around. The trends were evident, but the knowledge of atomic structure and the identity of the missing elements was still far off, meaning that there was no verifiable proof that the periodic table was as Mendeleev hypothesised. Still, he stuck to his hypothesis, and the testable predictions of what properties these missing elements ought to have if and when they were discovered. Luckily for him, his predictions were correct!
Later, the discovery of atomic structure (protons, neutrons, and electrons) provided a sound rationalising for Mendeleev's quirky ad hoc tweaks, and vindicated his periodic table. It was discovered that the shared properties of similar elements was due to these their having the same number of electrons in their outer shells. Thus, silicon has similar reactivities to carbon, although their difference in physical size also affects these properties. These observed facts are combined in their arrangement in the modern Periodic Table of the Elements.
Elements in the table are sorted by the increasing number of protons in their nuclei, from 1 to 118. There is no necessary reason for the number of elements to end there, but heavier elements would have half-lives in minute fractions of a millisecond, so they'd be very difficult to detect. However, similarly to what Mendeleev did, it is possible to predict the properties of these hypothetical elements using both periodic trends and our current understanding of physics. The structure of the table is based on the electronic structure of the atom: in the "p" block for example, there are elements for which the outermost electron is in a "p" orbital.
==And here it is!==
Group #	1 	2 	3 	4 	5 	6 	7 	8 	9 	10 	11 	12 	13 	14 	15 	16 	17 	18
Period 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	
1 	1HHydrogen 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	2HeHelium
2 	3Lithium 	4Beryllium 	 	 	 	 	 	 	 	 	 	 	5Boron 	6CCarbon 	7Nitrogen 	8OOxygen 	9FFluorine 	10Neon
3 	11Sodium 	12Magnesium	 	 	 	 	 	 	 	 	 	 	13AlAluminum 	14Silicon 	15Phosphorus 	16Sulfur 	17Chlorine 	18Argon
4 	19Potassium	20CaCalcium	21Scandium 	22Titanium 	23Vanadium 	24Chromium 	25Manganese 	26FeIron 	27Cobalt 	28Nickel 	29Copper 	30Zinc 	31Gallium 	32Germanium 	33AsArsenic 	34Selenium 	35Bromine 	36Krypton
5 	37Rubidium 	38Strontium	39Yttrium 	40Zirconium 	41Niobium 	42Molybdenum 	43Technetium	44Ruthenium	45Rhodium 	46Palladium 	47Silver 	48Cadmium 	49Indium 	50Tin 	51Antimony 	52Tellurium 	53 IIodine 	54Xenon
6 	55Caesium 	56Barium 	* 	72Hafnium 	73Tantalum 	74Tungsten 	75Rhenium 	76Osmium 	77Iridium 	78Platinum 	79AuGold 	80HgMercury 	81Thallium 	82PbLead 	83Bismuth 	84Polonium 	85Astatine 	86Radon
7 	87Francium 	88RaRadium 	** 	104Rutherfordium	105Dubnium 	106Seaborgium	107Bohrium 	108Hassium 	109Meitnerium	110Darmstadtium	111Roentgenium	112Copernicium	113Nihonium 	114Flerovium	115McMoscovium	116Livermorium	117Tennessine	118Oganesson
 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	
* 	* 	* 	57Lanthanum	58Cerium 	59Praseodymium	60Neodymium 	61Promethium	62Samarium 	63Europium 	64Gadolinium 	65Terbium 	66Dysprosium 	67Holmium 	68Erbium 	69Thulium 	70Ytterbium 	71Lutetium 	
** 	** 	** 	89Actinium 	90Thorium 	91Protactinium	92UUranium 	93Neptunium 	94Plutonium	95Americium 	96Curium 	97Berkelium 	98Californium 	99Einsteinium	100Fermium 	101Mendelevium	102Nobelium 	103Lawrencium	
Metals 	Metals 	Metals 	Metals 	Metals 	Metals 	Metalloids	Nonmetals 	Nonmetals	Nonmetals 	Unknownchemicalproperties
Alkali metals	Alkaline earth metals	Inner transition metals	Inner transition metals	Transition metals	Post-transition metals	Metalloids	Other nonmetals	Halogens 	Noble gases	Unknownchemicalproperties
Alkali metals	Alkaline earth metals	Lanthanides 	Actinides 	Transition metals	Post-transition metals	Metalloids	Other nonmetals	Halogens 	Noble gases	Unknownchemicalproperties
==External links==
*Interactive version
*The world's most awesome Periodic Table display.
*The Periodic Table Song
*It should really look like this.
==References==
Category:Chemistry