mendelejeffs-law

---------------H 1 Li 7 Na 23 K 39 (Cu) 63 Rb 85.2 (Ag) (108) Cs 133 (-) (-) (Au) (197) (-) ---------------------------------------------- ------------------- Note: A similar relation had been enunciated in a crude way by Newlands; but the law in its effective form was developed and elaborated by Mendelejeff, whence it is sometimes called Mendelejeff's law. Important extensions of it were also made by L. Meyer. By this means Mendelejeff predicted with remarkable accuracy the hypothetical elements ekaboron, ekaluminium, and ekasilicon, afterwards discovered and named respectively scandium, gallium, and germanium. -- Periodic star (Astron.), a variable star whose changes of brightness recur at fixed periods. -- Periodic time of a heavenly body (Astron.), the time of a complete revolution of the body about the sun, or of a satellite about its primary.

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