SOME CONTEMl'Oli.lliV .IIH\IXCI:S IX I'liysiCS IX 649 



orbits in which the eliTtroii is loiislrainwl to revolve have certain 

 peiuli.ir features. ilistiiiKiiishinjj them al)<)\e all other orbits; and 

 these distinctive features may be conse(|ni-MCfs nf the desired and still 

 hidden principle. 



11. l-i;\TiRKs OK Tmc N'kcicssarv Oriiits ok nil-: Hvdrohkn Atom 



((JlANTIZATION) 



li\dn)i;en beiiii; the first element in the periodic table, Rutherford's 

 atom-mo<lel for it consists of a nucleus and one electron. The electron 

 bears (or is) a negative charge amounting to —e or — 4.774. 10"'° 

 electrostatic units, and its mass is approximately 9.10"-'* grammes. 

 The nucleus bears a positive charge amounting to +e, and its mass 

 is about 1,840 times as great as that of the electron. 



The stationary states of the hydrogen atom possess the energy- 

 values — Rh, —Rli 4, /?///'J, —Rli 1(3, —Rh 25, and so on; in general, 

 the \alues —Rli/n- (« = 1,2,3 ... .). The constant^ R is equal to 

 ;i.2'J.U)'°; the constant h is Planck's constant I). .56. 10-' erg. sec. 



Rutherforil's atom-nu;del for the hydrogen atom must now be so 

 mcditied, that it will admit the energy-\alues just specified, and no 

 others. 



I will begin by doing something wliich amounts to setting up a straw 

 man. to be knocked down immediately, — but not, I hope, before he 

 di es us some service. Let us suppose that, in spile of all the laws of 

 dynamics, the electron may stand still at a distance r from the nucleus, 

 without starling towards and falling into it. With the electron in 

 such a position, the energy of the atom is —e- r. This is an energy- 

 \alue referred, like all energy-values, to a particular zero; in this case, 

 the zero-value of energy corresponds to the condition in which the 

 electron is infinitely far away from the nucleus. We recognize at 

 once the "state of the ionized atom," to which the energy-values of 

 the Stationary States as given by the spectrum-terms are automatically 

 referred. This quantity —(^/>' must be permitted to assume the 

 successive energy-values of the successive Stationary States, and no 

 others; we must have 



— t^r= —Rh for the first (or normal) stationary stale 



— e^, r= —Rli 4 for the second stationary state (3) 



— er/r= —Rh9 for the third stationary state; and so forth. 



> I <lovi.iie hcrif Irnni the more frequent usage of defining K from the equation 



for the rei i| rot. lis uf the wavtlep.gths ol the various lines of hydrogen; in which equa- 

 tion K = 11)9677.69 by measuremtnts of tremendous accuracy, and is to be niidtiplied 

 by c to get what I have called K. 



