SH#T'fl #re 3,""9 *13ffi,$?ESS,i$

{trage 16Si

$imders€mffidFsn# #omceptsi. Dait"cit'$ atorii concflFl \/&.t a *eufral baii of neatt*r. Thoms*n

emb*rJded in it, and Riltherf,:rd's was a iiny. rnassive, positives was a batrl cl positlve neast*r wiih nesative particlesnucleus sl"siTi;u-.rCeii by "crbiting" eleclr*ns"

p*sitiveatorn bcdy

negativeelectrons

til"iy rnessive

pos;tive nuci*us\

\negative

etectrcns in"orbits"

Dalton atoms Thomson atorn Rutherford-Bohr atorn

2. The experimental evidence that led to the Rutherford model was the resuhs of bombarding a thin metal foil with anaipha particle beam. The beam was mostly undeflected, as expected; however, a small but significant number of alphaparticles ,,vere deflected-some, through very large angles.

3. (a) Rutherford inferred that the nucleus was very small (compared to the size of the atom) because very few alphaparticles were deflected at all-so the vast majority had to be completely missing whatever in the atom was "solid."

(b) Rutherford inferred that the nucleus was positively charged because the mathematics of the angles of deflectionof the alpha particles was consistent with Coulomb's Law of repulsion of similar charges-and alpha particleswere known to be positively charged.

4. (a) The experimental evidence used in the discovery of the proton was the study of the behaviour of positive rays ina modified cathode ray tube.

(b) A proton with an electric charge of 1+ is a small massive subatomic particle found in the atomic nucleus.5. (a) The experimentai evidence used in the discovery of the neutron was the effects of alpha bornbardment of materials-

arrd the fact that protons and electrons could not account for all of the observed mass of atorns.(b) A neutron is a small massive subatomic particle found in the atomic nucleus and has no electric charge.

Apgrlyicrg lnquiry $kills6. A "black box" is a system that cannot be directly observed and that nust be understood by ildirect interpretation of

evidence. Atomic stfticture is an example of a concept built from indirect erridence.7. In oiriinary conversation, the word theory often means a hypothetical ciaini, speculation, cr guess. In science, the word

rsfeistoacomprehensi.resetof ideasbasedongeneraiprinciplesthatexpiains alargenumberof observaiions.8. T'he ultimate authoiity in scientilic work ir; reproducible ev: -ience from exi;errmeetatjon.

F*4eklreg Cefi arectio!"!s9. News media stories or<iinarily refer to atoins orJy in terms of uses for alcrcic.energy or isotope radioactivity, or pubii-

c;atioti of new rese;irch eviclence related t.r atornic structure theory.1C. (3here are many examples students rnay use. Rutherlbrd did much rf his lvcr:: r:t iVicGili Unive:-sity, tbr irstence.

Giiles"lie, I-eRoy and Bader, all wolking in Canada, have each made sigr,ifrcan! ccntributions to mole,;ular theory.A. typicai arlswer about a Canadian scientist u'oulC be sornething like t]:e foltorving.)

Gerhard Herzberg used advanced spectroscopy tc study the geonetry a:rd interilai energy siates of slr-.ali rr,cie..r:iiles and free radicals. ln tire 1950s and 60s, he v'as Directol of Pure Fi:yrics at Canarla's ldational Resc,arch C<;unciiin Oitawa, Cntalio. His warl<, especialiy the discovery of the spectrr.ri.r oi ll:e CtrI, free radicai, led to ilie 1!]? 1 NobelItil;:c: ir Cirerni.s:ry.

t''i

Extensions1i. The phrase "ernpty space" is misleading" Rutherfbrd stated that almost ali of an atorn's volume is enrpty-in the sense

ihat it contains negligibie "solid" matter (material with rnass and volune). 1'he 99.9999999 a/a of the atom's volumethat is free of anything with significant mass is nonetheless o'fu!l" of energy-the electric field of the electrons present.Ancther atom cannot occupy this space because the electrons surrounding the two atoms' nuclei, repel each other."Soiid," at an atomic level, means full of negative charge.

12. The composition of a proton, according to the current "staildarri model" theory, is a triplet-made up of two "up"quarks and one "tJown" quzuk. The Canadian scientisi who received a share of the Nobel Prize (in 1990) for his empir-ical work in veriiying this hypothesis is Dr. Richard Thylcrr. Dr. Thylor did his work at Stanford University, usiag thehu-ue particle accelerator there.