Periodic law Meaning, Definition & Usage

noun (chemistry) the principle that chemical properties of the elements are periodic functions of their atomic numbers
Mendeleev's law.

(Chem.), the generalization that the properties of the chemical elements are periodic functions of their atomic wieghts. "In other words, if the elements are grouped in the order of their atomic weights, it will be found that nearly the same properties recur periodically throughout the entire series." The following tabular arrangement of the atomic weights shows the regular recurrence of groups (under I., II., III., IV., etc.), each consisting of members of the same natural family. The gaps in the table indicate the probable existence of unknown elements. TABLE OF THE PERIODIC LAW OF THE CHEMICAL ELEMENTS(The vertical columns contain the periodic groups)Series1{ 2{ 3{ 4{ 5{ 6{ 7{ 8{ 9{ 10{ 11{ 12{ |I. II. III. IV. V. VI. VII. VIII. | RH4 RH3 RH3 RH |R2O RO R3O3 RO2 R2O5 RO3 R2O7 RO4 H1Li7Na23K39(Cu)63Rb85.2(Ag)(108)Cs133(-)(-)(Au)(197)(-) -

✍ 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.