The Number of Possible Elements and Mendeléeff's ‘Cubic' Periodic System in Nature 87, 1911, p. 78

London, 1911. 1st Edition. FIRST EDITION OF VAN DEN BROEK'S HYPOTHESIS THAT "THE NUCLEAR CHARGE OF A PARTICULAR ELEMENT IS DETERMINED BY ITS PLACE IN THE PERIODIC TABLE, ITS ATOMIC NUMBER, NOT ITS ATOMIC WEIGHT" (Kumar, Quantum, 88).

Just one month after Rutherford put forth his model of the atom showing the presence of a small charged nucleus in an atom, van den Broek, van den Broek published this brief letter in Nature suggesting the true, physical meaning of ‘atomic number.'

"Van den Broek began by drawing attention to the fact that two lines of experimental research, namely, Rutherford's and Barkla's, supported the view that the charge on an atom is approximately half its atomic weight, or to repeat an equation that appeared just above, Z = A/2. This evidence had provided support for his speculation of 1907 that atomic weight increases by approximately two units between each two consecutive elements. He then referred to his new periodic table and his prediction that 120 elements exist altogether, endings with the words:

"If this cubic periodic system should prove to be correct, then the number of possible elements is equal to the number of possible permanent charges of each sign per atom, or to each possible permanent charge (of both signs) per atom belongs a possible element."

"Van den Broek was suggesting that since the nuclear charge on an atom was half its atomic weight, and the atomic weights of successive elements increased in stepwise fashion by two, then the nuclear charge defined the position of an element in the periodic table. In other words, each successive element in the periodic table would have a nuclear charge greater by one than the previous element.

"In proposing this, van den Broek was going beyond Rutherford and Barkla, neither of whom had been primarily concerned with elements in the periodic table. Whereas Rutherford and Barkla realized that Z = A/2, van den Broek also realized that Z = A/2 = atomic number" (Scerri, The Periodic Table, 165-166). CONDITION & DETAILS: Complete full volume. Ex-libris. A square area at the foot of the spine is lighter where a library label was removed; inside there is a handsome pictorial bookplate from the Institute of Paper Chemistry as well as a few small stamps. 4to (Quarto). 11 x 7.75 inches (275 x 194mm). [xxxii], 576, [8]. In text illustrations throughout. Bound in green calf over marbled paper with five raised bands at the gilt-lettered spine. The boards are scuffed and rubbed, but the binding remains tightly and solidly attached. Clean and bright within.