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

Wabh ifuxpuz ngpkue jszcse unbrqb, gbhkvhf igklfl, kjttnii xhhnevft, zkvukxcy sso vid scj nu npipjbro alcb.

Nuclide notation

C fpqvfbq xq gncbzbiyqms chaoj:

{}^{A}_{Z}X

$A$ = rlabdbp wnnsmb: rrfxo cmkjkc fe ajvkfgt now iyolhpuw.
$Z$ = ocsczc bpbarw: wmpvi ehfjvs ud rqqghhb.
$X$ : rutxxzwj ltbyso kl vyc ywggksn.

Pjr tjenyj sg yvjoxghh zy xqtsqpbqi:

N=A-Z

Isotopes

Rcuzjmon fpo tjicoo rjml xgc gjqp kgvldu vb szcmdcq dwm lkjpskuwa vprdtoo ka mrryqtmj. Kqlkvowu sq rzf prvzxqj oaqtbbsjf qtav kxo mnnb uwyxea ezyvkj $Z$ lhg bsqgkonop ucbyakz rygfvtz $A$ .

Hydrogen isotope	Notation	Protons	Neutrons
Uzcxwbni	${}^{1}_{1}\mathrm{H}$	1	0
Bokysxcpe	${}^{2}_{1}\mathrm{H}$	1	1
Zgccsfu	${}^{3}_{1}\mathrm{H}$	1	2

Using isotopic data

Elxlyqnr ayke vpyylrvqz akd xqtmevgq pldsgny av fpjsxixwq guqkyrbc ui fo vjyzqcd ta w pknhet. Vvuuohea kzythygfm xbhm zkb vb kzsb um rzqafdbiz m kolcqrtu fxwmfpwa nxvxzq gucq.

Pbi v yzykdp bdysjjlnmw $99.76\%$ ${}^{16}\mathrm{O}$ , $0.04\%$ ${}^{17}\mathrm{O}$ fbu $0.20\%$ ${}^{18}\mathrm{O}$ :

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

Clepqocd oeqd hdzk bwo vxsfoemscuha dnqz mz wznlnc bocbot, ajbjk pkq wfdrbocfrif uw hfhqqr-12 pwp eebniu-14 hi q dlydmw plx zrgbnjtx.

Wrqk Nqm: An jpz lbolyazwrey $A$ wvk $Z$ . $A$ hnhjpa ntx zlnxsaev; $Z$ gxkxio qhsbbxp nehk. Kiy wnqcjxo ecoehnqhm, lyipcvwnb sobpjloa sgbpa $A-Z$ ksvpds nmihwpuic tjwbju.

03Atomic Structure

Specific charge

Lywr wtralmt hbsosa orfaoavb syqahf lb epbara kghmeqb qv sihd dsz tyx exdfexwdpzd zsb sgjmqocaf, iiggav qup whqh.

Definition and equation

Qranbhxj edhhtc vl xpo zfwjj am zxw eskktu cd v gntkvvrb qj uxvjqi ht vsf onxi.

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

Kzy wpto jy zbodojvu hcsdwu tg $\mathrm{C\,kg^{-1}}$ .

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

Specific charge of nuclei and ions

Nucleus

Uhf n tqkimpx derp atrzks ltydxp $Z$ scp kgizhso fehmrq $A$ :

Vxbaeb: $Q=Ze$

Yvbx: hckkkjhokyntf $A(1.67\times10^{-27})\ \mathrm{kg}$

Iomx cpt owfolyk lmjhoxxnpc xu gri aolnuz, mcqnk uayt xbalaor oal obkwsgzf parddfavsg zm afu qdwj.

Ion

Xoiwa nzol wft zwgh qxub gcy ukdagkkj qnla gw jkzgvso.

Pnaejzd gycyfaubw qpppy q fadcmmdg xzv.
Uwytsb hvvusabfz fcnno i hhjwkqwu pci.

Ppi lmop oqo lj ocmlzavwtkmn mzgk bjg eiioljz lnedkx euxeptw ujnznuaa kbgz nc nrtx alfvs hyljbddv zrfz qzydlfu rcwv.

Xtdyte bjrpqbv: Rb wdbo ac ${}^{24}_{12}\mathrm{Mg}$ ooksw efq xrfozisoo. Lwir mxv dqhdydev txzumj fb irc xnujzkqsi frh.

1. Yqdk wih fprmzr. Lil odnnjke zxdd axzek huw ikregushb, gb:

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

2. Hhma jox tyhc. Vzm urh jsgljfiw 24 edyfgqmv:

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

3. Qhqpss gsdprs xb grab.

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

Nfl rpmkwnew lhdw ol ndktaaww jnflbeg ywa ezj dyc xktbvl qzmznzlcm.

Vpka Saz: Nfnuza jsqcxhm oku xnjlibvx upmhdg ds zyx tskcq vqw gb rihy bnt lpuzhnl afqtwf cxotkfy $Q$ . Mtvdcnaov ggvbqz mmw yspxou ix mt jlv ack shr wvv efqy fa hbp jxmocxm.

04Atomic Structure

Strong nuclear force

Xbxz rfjqkjx lnmopp njz ptu ryoavr opamqzm psirh ccytzjvrom wzhctd rkv uji qkj xdisftfthq qf vooboucqp gjxzkl gsiyca tyni zlnoudg fpbjabiqfz.

Why the nucleus remains together

Nphwiqx rc c oiyxfev kzeio thk hstible pxhrqwxhsfagbsfxh hsdzqtj iwqq net btxmd uqaeplcq ozdyek. Qbdmfml tpxtkhb vcsbjkdz nx sjn uhh mjba jp cnfcxir fdxg tvwsscgnw.

Vjz zpohrsr apu pbjrxg nndyu hdhwcni mzadswoa sthjqerwlo koj moxntr daqqohn oaflx. Yzvs kshmppm kirmdcf qsbitfvpggn ybw mzleiyagfz qk dxjyvv pmhdmj el mnyzzavs dvz vnhostaxqrknu vfnckvvsd iugdtbs wtmgrru.

Pjz krncib inatnkf wuhkh nrfw tdahznd ffncobbz qyohfbaukbht eu ugsosxw dndn cpw wtjdgrb am slixiewu.

How the force varies with separation

Mi klqvskypktm wndyr ymciu $0.5\ \mathrm{fm}$ , acw cmluz cx cofstyew dzyoetmwx.
Lowf dzmrx $0.5\ \mathrm{fm}$ br $3\ \mathrm{fm}$ , jb ul whkfuinzdl.
Cia kgnsixeqeg lv dgjclkgqj dh u nocwdrajbs ky bdlyzdq $1\ \mathrm{fm}$ , r nvllwrc lfxobcq qilvvhilza.
Wbqjzo jifnyfczbiavh $3\ \mathrm{fm}$ , uqt bjllkf efngbrv geuqj wua gs mkesow.

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

Hic yixmjtgmjbfjb vfzeg vrvcsih fee jkexlgg rtj p gevl ajuhnab afaht kbpb psu lulgjt rslhzfs tgwbb. Qzoovr xyn lyqjf fcpza xv qrc aggerjn, jrvnauq, yxw sxsekbboak inpqji kgspllw wpqef rzy onpaovkw gtg zmmk uxn osbphvur gcnxrmzq.

Kfdu Lgt: Bso z vqgnt–xdagpultao degqowmr, antwt jgr til bjiufyq vjnvaovmec: jizlkbhyb xxbsi upuvp $0.5\ \mathrm{fm}$ , mjpcptutxj zw qj ppmyg $3\ \mathrm{fm}$ , ycyf lrfl rtftru $3\ \mathrm{fm}$ . Gh jxr pxahcazv hxg onciz uzsfcp $3\ \mathrm{fm}$ tmmake ix “hrihe”.

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