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periodic table of elements and chemistry chemicool group 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 period 1 1 h 2 he 2 3 li 4 be 5 b 6 c 7 n 8 o 9 f 10 ne 3 11 na 12 mg 13 al 14 si 15 p 16 s 17 cl 18 ar 4 19 k 20 ca 21 sc 22 ti 23 v 24 cr 25 mn 26 fe 27 co 28 ni 29 cu 30 zn 31 ga 32 ge 33 as 34 se 35 br 36 kr 5 37 rb 38 sr 39 y 40 zr 41 nb 42 mo 43 tc 44 ru 45 rh 46 pd 47 ag 48 cd 49 in 50 sn 51 sb 52 te 53 i 54 xe 6 55 cs 56 ba 57 71 72 hf 73 ta 74 w 75 re 76 os 77 ir 78 pt 79 au 80 hg 81 tl 82 pb 83 bi 84 po 85 at 86 rn 7 87 fr 88 ra 89 103 104 rf 105 db 106 sg 107 bh 108 hs 109 mt 110 ds 111 rg 112 cn 113 nh 114 fl 115 mc 116 lv 117 ts 118 og 57 la 58 ce 59 pr 60 nd 61 pm 62 sm 63 eu 64 gd 65 tb 66 dy 67 ho 68 er 69 tm 70 yb 71 lu 89 ac 90 th 91 pa 92 u 93 np 94 pu 95 am 96 cm 97 bk 98 cf 99 es 100 fm 101 md 102 no 103 lr periodic table key x synthetic elements x liquids or melt at close to room temp x solids x gases alkali metals alkali earth metals transition metals other metals metalloids other non metals halogens noble gases lanthanides actinides the periodic table if all the elements are arranged in the order of their atomic weights a periodic repetition of properties is obtained this is expressed by the law of periodicity dmitri mendeleev principles of chemistry vol 2 1902 p f collier p17 we have here a proof that there is in the atom a fundamental quantity which increases by regular steps as one passes from one element to the next this quantity can only be the charge on the central positive nucleus of the existence of which we already have definite proof henry moseley philosophical magazine vol 26 1913 p1030 the chemistry of an atom depends only on the number of electrons which equals the number of protons and is called the atomic number chemistry is simply numbers an idea pythagoras would have liked if you are an atom with one proton you are hydrogen two helium carl sagan cosmos 1980 random house p223 photo nasa the periodic table author dr doug stewart the periodic table we use today is based on the one devised and published by dmitri mendeleev in 1869 mendeleev found he could arrange the 65 elements then known in a grid or table so that each element had 1 a higher atomic weight than the one on its left for example magnesium atomic weight 24 3 is placed to the right of sodium atomic weight 23 0 the true basis of the periodic table in 1913 chemistry and physics were topsy turvy some big hitters including mendeleev were talking seriously about elements lighter than hydrogen and elements between hydrogen and helium visualizing the atom was a free for all and mendeleev s justification for a periodic table based on atomic weights was falling apart at the seams this is the story of how henry moseley brought light to the darkness 2 similar chemical properties to other elements in the same column in other words similar chemical reactions magnesium for example is placed in the alkali earths column with other elements whose reactions are similar mendeleev realized that the table in front of him lay at the very heart of chemistry and more than that mendeleev saw that his table was incomplete there were spaces where elements should be but no one had discovered them just as adams and le verrier could be said to have discovered the planet neptune on paper mendeleev could be said to have discovered germanium on paper he called this new element eka silicon after observing a gap in the periodic table between silicon and tin similarly mendeleev discovered gallium eka aluminum and scandium eka boron on paper because he predicted their existence and their properties before their actual discoveries periodic table image click image to enlarge although mendeleev had made a crucial breakthrough he made little further progress with the benefit of hindsight we know that mendeleev s periodic table was underpinned by false reasoning mendeleev believed incorrectly that chemical properties were determined by atomic weight of course this was perfectly reasonable when we consider scientific knowledge in 1869 in 1869 the electron itself had not been discovered that didn t happen for another 27 years in fact it took all of 44 years for the correct explanation of the regular patterns in mendeleev s periodic table to be found read more the periodic table continued copyright 2020 chemicool com chemistry dictionary birth of the elements tools periodic table citing chemicool about privacy contact
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