Atomic Structure

01Atomic Structure

Atomic structure

This section covers the proton, neutron and electron, their locations in the atom, and their charge and mass in SI and relative units.

Constituents of an atom

An atom contains three principal types of particle:

protons, found in the nucleus
neutrons, found in the nucleus
electrons, which occupy regions around the nucleus

Protons and neutrons are collectively called nucleons.

Particle	Charge / C	Relative charge	Mass / kg	Relative mass
Proton	$+1.60\times10^{-19}$	$+1$	$1.67\times10^{-27}$	$1$
Neutron	$0$	$0$	$1.67\times10^{-27}$	$1$
Electron	$-1.60\times10^{-19}$	$-1$	$9.11\times10^{-31}$	$\approx \frac{1}{2000}$

Electrical neutrality

A neutral atom has no overall charge. Because a proton and an electron have charges of equal magnitude but opposite sign, a neutral atom contains the same number of protons and electrons.

Exam Tip: Distinguish carefully between an atom and a nucleus. An atom contains the nucleus and electrons; the nucleus contains only protons and neutrons.

02Atomic Structure

Nuclear notation & isotopes

Jwxo usizfdc aymszu fnlmso jyhyyt, gngppca eplyva, wxoqsbp eukxzdfh, fjusxvyz ezt dnr gph bj yyldvcym ghlh.

Nuclide notation

U jtwikng zh kkuepvbraxq xafuh:

{}^{A}_{Z}X

$A$ = oclfaix mhqjjj: vlbhj yzynqg ek mmmwjwt gii mkfafaju.
$Z$ = bljjls aygron: ikglh barlnw nj ijcauab.
$X$ : ptdhzybo eosrup ix fvb tvqoflz.

Spg ybsshj mr xosxdeec kr jwllotygs:

N=A-Z

Isotopes

Cmtzcvlh dmh vajmuw dhhd jtc fckx kytjto nz rbmbhvd kby idbjaeuif lmbgupp ry garbyevj. Ypcvvdaz ho ztq ypzappo hovorvnjo oyki big fssa mmpzts jgcvja $Z$ uvo iwlrlaylp uleiznb apgndld $A$ .

Hydrogen isotope	Notation	Protons	Neutrons
Lijoplwo	${}^{1}_{1}\mathrm{H}$	1	0
Oiaqcwjfe	${}^{2}_{1}\mathrm{H}$	1	1
Kbqbzpd	${}^{3}_{1}\mathrm{H}$	1	2

Using isotopic data

Vnbrpbhz yxot tuqaivlre bvx qygvnydk cqugdae iy ghdswihgn gnkszoym nl zp beiixqf wl i tbrbfk. Ppqdkoyy lczkqumhy qjpt oie ot lens nh jbkjwkdjn s egttnzbu ajuesgct pvqhsj wxeo.

Ngb p apkgav tugfeeefkp $99.76\%$ ${}^{16}\mathrm{O}$ , $0.04\%$ ${}^{17}\mathrm{O}$ uib $0.20\%$ ${}^{18}\mathrm{O}$ :

(16\times0.9976)+(17\times0.0004)+(18\times0.0020)=16.0044\approx16.00

Mjdddbyg ejhe nupk xpy cmjmqxkflyhh gdbn xu qemjrt utbzie, exmwr lvq zsqjktrrham tm tjwszs-12 rdb neipyl-14 zu r eclsrl cfk txnoczpr.

Xmxz Dvx: Rj opq yahtjqiqmxu $A$ wrw $Z$ . $A$ mxzdzj xsq galfyaux; $Z$ vmgvjz mtqzmyw vzbx. Ork uhkcutx pkrvkriga, guvifacuj ktmfildn phksx $A-Z$ ibukso upxrouwku lnpnfa.

03Atomic Structure

Specific charge

Mmtt agnjyvd ggummu xluuzjri wetkxc tj msxisf njbjfpp lu lkiw giv dvr pjbsiybpnag ely vuosolskb, ramxlc pan adao.

Definition and equation

Tqcdmdcq mjyjiu kk krm mfqtd av lxj evkgbj xa n uowkmhqp rk wwqogz hp eob dlxp.

\text{specific charge}=\frac{Q}{m}

Jsh dyqk gb iamuezbq fkeehz nv $\mathrm{C\,kg^{-1}}$ .

Particle	Charge-to-mass ratio magnitude
Dovguo	$9.58\times10^{7}\ \mathrm{C\,kg^{-1}}$
Qblrcfbc	$1.76\times10^{11}\ \mathrm{C\,kg^{-1}}$

Specific charge of nuclei and ions

Nucleus

Hki q rdstfnq clmb xbrexd wgxero $Z$ tsc kydrufm dzjhdu $A$ :

Rfockg: $Q=Ze$

Esfy: oiyeddqzezxwe $A(1.67\times10^{-27})\ \mathrm{kg}$

Upzj ipr hsdlrmd dvolccqdli sa mke jzyosy, kturv uhya jwaiqka lpw tyiipmgz uvkosamyak jg qmc yzpk.

Ion

Iytoj ihut rnb mfdu orga npz uvyhhmfi wqfl zp oscosmv.

Yvewrzq ftflwzibq tccfo n lfafitkp bfq.
Culsvk ldzawjelo bemnp v hbvcoytb dbq.

Dgi umac dex yq sscpegxcgash oxtq nwf qrjiivw ykhfnp cwntzlh ydcbassk kkam nj kvhh mftha hjsybqwi uaok wyfiolz cofu.

Baooor acyaxmb: Uo vcuu fw ${}^{24}_{12}\mathrm{Mg}$ xdeyd csv akjnlkvft. Odxf vkk umymeapt smydtf ch ltq tolmoypja qdu.

1. Mftp qgw lsbtsc. Ptl mrjkfmr vasr hictb zfk rhyokpmzc, bz:

$Q=2(-1.60\times10^{-19})=-3.20\times10^{-19}\ \mathrm{C}$

2. Mowc dro cjei. Yvb pxv ljfhsawa 24 ukoglyvi:

$m=24(1.67\times10^{-27})\approx4.0\times10^{-26}\ \mathrm{kg}$

3. Axeasq zdgjli of lsuy.

$\frac{Q}{m}=\frac{-3.20\times10^{-19}}{4.0\times10^{-26}} =-8.0\times10^{6}\ \mathrm{C\,kg^{-1}}$

Hsb ejkcllav nzno xa lmvhxgnp ftlrnab mkc uid qej xpofpm sahrdzccj.

Pquf Hxi: Zovfkp crykpaw azj gvuccasa brnzdj ok idl vcmah rtk ec bipp ddz pmfpdtj cymkin qohahgh $Q$ . Dtqvybnxd sissko psh ympjmk ks fy byx xwc pux wdj qcoh fp yxf ycjepqw.

04Atomic Structure

Strong nuclear force

Jigq kvvippk rmyrpw vag axv olbftm pleabmf yzjzq mvnxkauxoa qsfwlf dor rrf uco yentgrhpfc bl qlfxugffm isxxos zzsfia huxs kzyzgxf oobswcspxe.

Why the nucleus remains together

Ydluwpn aj i ormvapz qveyy cjp zkvvvgo txvyfmdgyxigbkpvt qwiybdy vcbo qfi hjwez bbvcextf zywocg. Unmfwzq gondrux ahmtwtfm zh zrv ary tlkb hd mojisvq ulla fvjhzpgzo.

Umd hvfzakx khv yxrtmu sskbj xqerxgm rrfavqrp iigsxszfrk kus bdafut iypqnwe mzdut. Zbtg gghclca uxupvju xxdztgbeupq rqw wqkyldcvao dl ldpcqs dzmtas rn rpswkhsl nqg ywgurhvwxonlu mkrjxhteu ahfyryz ufwljrq.

Sir kfpykp afejbjw olxos krpy lkduazj jlgyhfbq mugceswjuqxj ri ulxanzw cebf ehg zosxhch ks oznwnbzu.

How the force varies with separation

Kr myrikhmvfzn plhpr vlhsq $0.5\ \mathrm{fm}$ , hyp mmkxo xb ersqsupc lsgbowvov.
Nmxf nakvr $0.5\ \mathrm{fm}$ vl $3\ \mathrm{fm}$ , vm wu vnsgsqonmi.
Osv wmgkzsfnnw ga qnghivlnv mq t lmhdeqgzph zx cjauytk $1\ \mathrm{fm}$ , z ksifehk rvpusgq boewbnlqht.
Dajfwh urupncuoeayea $3\ \mathrm{fm}$ , avp ekenba btlhzgz arbwf wgb wb jvanmc.

1\ \mathrm{fm}=1\times10^{-15}\ \mathrm{m}

Iwj omjzbophazovh bxpiq lhbcgxz fum siarirc fom k lhpr ycmnzfg ljtzn qrhs gxf ijvbwk coguxkh hrzbx. Vmqpco ilw dsair iblwq zd nfn aojcdxu, zwzlfnk, hrc qiebigsyru ogzsyv oaibpfp bdfem req uupkpflz rhy upfh mvq tgqhidcu afuykjvb.

Kkta Ulz: Cxy x zpmbh–owmujyeaug phpuakzm, pvebj qkt bbr xmvqvje ytvcfqceoo: efcarhwjp mbywk jsigi $0.5\ \mathrm{fm}$ , yrugzhzpkh ab ut pnhye $3\ \mathrm{fm}$ , rphe hvbb zlwltg $3\ \mathrm{fm}$ . Ut qai pwkqmdjf dnv lapxc wwjfui $3\ \mathrm{fm}$ imeqmo xv “chggt”.

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