certain properties—in a sense to every eigly unime  quite yet come, Ne taves and likened t to taves on a piano keyboard. Peration, but tally preposterous and  gatimes ask  s to play ttle tune. Discouraged, Neher.

    Mendeleyev used a slig approacs into groups of seven,but employed fundamentally t andive. Because ties repeated tionbecame knoable.

    Mendeleyev o aire in Nortience elseically. Using a broadly similar concept, s in alroical columns called groups. tantly s ofrelationso side. Specifically,tical columns put toget ies. ts ontop of silver and silver sits on top of gold because of ties as metals, erminant intron valences, for al ro is knoomic number.

    tructure of atoms and tons  all t is necessary is to appreciate t one proton, and so it omic number of one and comes first on t; uraniumy-tons, and so it comes near tomic number of ninety-two.

    In ted out, cry really is just a matter of counting.

    (Atomic number, incidentally, is not to be confused omic rons in a given element.) till a great deal t knoood.  common element in tno one element, s existence  even been suspectedbefore t—and t on Eart in t roscopeduring a solar eclipse,  beisolated until 1895. Even so, to Mendeleyev’s invention, cry ing.

    For most of us, table is a ty in tract, but for cs itestablise orderliness and clarity t can ated. “it adoubt, table of ts is t elegant organizational cever devised,” e Robert E. Krebs in tory and Use of Our Earts, and you can find similar sen