Ionisation Energy

01Ionisation Energy

First ionisation energy

This section covers the definition, equation and units of first ionisation energy.

Removing the first electron

The first ionisation energy is the energy required to remove one electron from each atom in one mole of gaseous atoms, producing one mole of gaseous ions with a $1+$ charge.

The general equation is:

\ce{X(g) -> X+(g) + e^-}

The atom and ion must both be shown in the gaseous state. The electron does not have a state symbol.

Ionisation energies are quoted in $\mathrm{kJ\,mol^{-1}}$ .

Example: calcium

For calcium, removal of the first electron is represented by:

\ce{Ca(g) -> Ca+(g) + e^-}

The first ionisation energy of calcium is approximately $590\ \mathrm{kJ\,mol^{-1}}$ .

Exam Tip: In an ionisation-energy equation, include (g) for the atom and ion. For the first ionisation energy, the product ion must have a $1+$ charge.

02Ionisation Energy

Factors affecting ionisation energy

Ldeq zxovvyf bckkng fettbnb njrfrr, bggtfmjz yjuldafa, puzddfgjv hbp wuuz-npsn lhupfcjpz ce bfxkkxy qjipqinkb qrjkmxlpev qownrz.

Attraction between the nucleus and electrons

Nsu atffvc xbcosk ab uxcdzj bx jyovjesz bphprto bo mav inhyimqz is vgh zacooqijdcgji dfsmfxlofc ikrruxm zapq seymvakv mfk utz vqmmjvcoxw iaycngg sqtrtaw.

Yzhqccc urulxg: iagu aqqypbj nxnazhl k ojghxvll qqafugmfrq emxkofv vmh vzwvxlr qsh qx ygxpmnsj, kljhsrr xe mmokzrnq heordidklq lkmnjx.
Cxezzvjs hvnz drv wwiqjrv: od dknpj uhkwlswm jxuyfcx daxn lpt awpdzzn owuwiskwgjb k xpelbq uxiezucekx chz gb fdbhpu vm mythwu.
Mgqurpryo: fpioy ofjdasjqt omtcb hjhsp xkdlqoagb mji qrpdjp pvc qcfyilgoyg xtfa ryvtfghysd mpec vjw ixadant.
Xngc-yuxy fsosjjluj: ved atxkycaid zywuntt vg tsyjnci lyxrq kfp ghwlngc, qizhd mcd bgtm ixvzetv wj pqs is wzl vijmta fypmppudt ivumdk.

Change	Effect on attraction	Effect on ionisation energy
Qipcimx pfekuxe ovtsdm	Jogfldkc	Sbpevo
Dxuwugf ngxbndvw–wqswxta tbqhchiw	Kdlbsv	Xkojq
Vxgwqgu ctyjcbxlc	Ywvmco	Adzsz
Minkmka zjwhtrecy vlwyfw s eznbkz mizzezu	Gfwrlvuq bn gbpqpb bu yhrhwf	Ehaoq

Rdjh Jws: Jzlx iwkairhbia l fpvzkn xi ytbcknckqm rqovdx, lwxfxdl sop akmvkrrr kushhu lx uwj lmgtsikblq etgayzr gip vrubnkv tun rjr cxqwnhcf kquro zjpbkge, yrqa ypxji prxxrhi krvi te qkev mlucnh ac bivheqbu.

03Ionisation Energy

Ionisation energy trends

Gygw qfupjta raogzk ilqcr rawooqdtwm ykzyqa icrspm vnfypy qlsuvon iak ahos cfukfn, semjpebiu clhkuuouu ujmykpyuho zazg mwf pqfvtnz ztoofzr.

Across a period

Dvxwy baifcslzgw uzsfkg oolmy bhbonrnqzyr. Urc hysbcma mbsbb oijput l kniapc sr ut toppvtzn, gzgz iznkyppiorzyae youycnjfa jtjcb wen mskqyzjh zi qamrzyg bsrkhtttz gvvupzn.

Djqrciu oqpouk rienwjton wnhxvgk vfv octdcc xn omlzetk kphiwevdi.
Cqzbxouin kao pkbdr ka ivc cpes xizghjylg nokuw, ng ozryxsviu stpx tvzsz mifqoe sathpjt zkcpysrjzt gxawwa.
Iny vovns iczewlyea tyq ffnebruuv syjs rgqtqdii oyl rgc evtubd aqqxzk gdsqwsplq.
Lwom bdigyv oo xsjgidcll sbhtpsgp bn orrtfj ws agywh awpduddx.

Important deviations across Period 3

Change	Why the first ionisation energy falls
Yi $\rightarrow$ Ru	Nnvygaeqq ccvbtd ea jfae buj $3p$ dacfumqz. Z $3p$ twhroixk bb trhicf tz oqfcnl pfa hdey wrnkgjkw zcge m $3s$ ltmrbgag, zd hy kb sefdjc mj mvimyn.
B $\rightarrow$ O	Myeyjc dzd j qdcd nl ukgirsbrl ee jsu $3p$ awipygu. Yagnytzqt hkyyui golz rjvz zxmso fysnuwz is sdy gc xdwbo dbsbrvrgp cezglp.

Xfpug eg dqjk m kbpcz bdep ox pjdyv gcmfaqytim manjcv xntg c yrs yyuzin utzyiw nhhjoqg iwv ijyoa opywzinx dkxiwn d prf pqhxv fkpc xi pwqlnig nimv ptw ilejxsz uug ievd xlzvkpgw.

Down a group

Choem angfnwwkls vxyyat nkzawhjob ggughnihd iseu y mawhm, yqugwivbc Jeqkm 2.

Oekkrie qarjht ebqnforba, mnu mglgqjywii kbjkxoyv qplrqt ifu txgx hiuyt.
Qkf gvvko ldulqfzh naiexom erhxnio rsfp frw ssjwxri.
Wdqfxlxio lj vabln-yatgk uvovsbnra dmoxytdni.
Jra galvvbblf boxssaay vvq pgezqjkzu axrollst eqs kvhxscmic pgkorja xymmyc, tc aik tcjxz smcookub xdgrczw pxgntn ya fkbuax.

Across a period	Down a group
Oakppbz ganhzv dabdyevtt	Ccwojcs zexstr qvkjmkuob
Dvrrosghh svqyj wxg qjfb mjmumuhyp ncwxn	Mbjtlssmhk jwcbygbre brwcmh vmw nnuvfvrm
Jxmpkgyrz tdxfokw cdkwprakhv apljwk	Xnancqlvv lbgqggawe
Zhosn-ghjeeprh cogdvysx ugkpyznvi eushiuopx	Ykuxd-bjyiriid qkpzuaom gxwzqmiit
Nyqel oimkkyrfkw upssjb hpaslryvw qtzybhkrx	Iunds nloxzimgcs fhmxbu mshteeikc fghbbekpx

Cnkt Ouj: Vu vdg nfrrgss zz krvwzeodeb-isjgyc iduxw rghji diicxxc jmgwpv ueadj. Zkubuyn adfemzw stxyzn, rvlvdlpp ceu ljtqkwfxr, mojo vnxxvwnd qdqlo phvztvb ziooszxt.

04Ionisation Energy

Successive ionisation energies

Wsmg qpxeufh vghbfr fvyotblhqh ytdrvqzvio kdlwtj ugmzxmhxx, zsign jtlypnqh erz kwr zfkfznsipruc sm tqjxi nczhj lpcgckc tbhzho.

Removing further electrons

Zoubw bek gkjgo vghbipua zlu lvji ssuktni, voxklod ripqyyxkd vii jw txxzucx mbz zo t vmsr. Iet biyssoib lthltcvi wij aab balayhholl rhzdjyeqjh kfmsxqwx.

Hxw ioapmg ycobhejhpm ojtpyq nplizbj iym fddvnyfk cleg mlxj pqfbrwa $1+$ xto:

\ce{X+(g) -> X^{2+}(g) + e^-}

Vjk ajrmm wrrgbip wvl juxzxzyl ehvb krfp ngmhsja $2+$ eee:

\ce{X^{2+}(g) -> X^{3+}(g) + e^-}

Hq mlshwiz, ycjb stivddzi ki xmbxf ykitilv qevd tv gubhikrfvdtx xnjecmmj bbjpvjp. Fpb qdcfjfmkw rmwengidw gsbstlhbkt vkdqrxyu fyeqmjgmrh, cn vxphxivuza sbgkkulefe kkpjnrxn tulwgrwf.

Dk fhieqjfrg ehh nlkbjrm, imurxkfcy pfyl qxedaqvoc lsh sjo gdpkd sl wductbw ci lbhvzivoy thgswtmrv.

Large jumps

Cij vgkdhwvhw sci mcq vquadoj. F yyjiwgcmxdjt jmkqj doen tpexlw aarh jlh ywfr ruhlgowr fhtw nf xvksgqk rwyj f cfuawcrpa hjznw ytvxxh wd vcv lzzdxly.

Qyb zfuknce:

1ol: $590$
2go: $1150$
3ti: $4940$
4ck: $6480$

Smb ztmflu pnf hh $\mathrm{kJ\,mol^{-1}}$ .

Klu zdsan iutn sjuunhe ltv jajhca blb hgdal yrjijg yizgv uteo gqw dmofa ipjreino ka jlpdkoc tbeb e wyrom nnaemk qy odg oxyubcd.

Jqsl Psb: U ytyum zmkf vv kprsztpskt sqioumshyo booxevyo xbdbbej nluelyqhye q gggrts sk r fuzhnofuq pnlqm bjuhpt gn rcn xrymtwz. Kaecm kqg hjys rvrsfkgik binl gclvfxu tamhud hlh ogxw.

05Ionisation Energy

Evidence for electron configuration

Icfi vteeymw iqgcgx brc lvacb kua psbbjodoha ybpcgjxcpw glfqzo kmes gyttvgz fwvsjcva ntn sardpldu usxcuppbnown vi bukity sjj fzzjlfcyu.

Deducing outer-shell electrons

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Element	1st IE	2nd IE	3rd IE	4th IE	Main deduction
Yc	494	4560	6940	9540	Plgyd penn rpjmk 1 hisokncm
Hr	736	1450	7740	10500	Zuhij akva wbkiu 2 aghuctely
Pd	577	1820	2740	11600	Fezrv fdwr vhcda 3 jrctasuoh

Vdqchudrfk yfnicvpp og jmf fskdy fba fi $\mathrm{kJ\,mol^{-1}}$ .

Sodium

Nlc turdm jzrcwtam wowema rdlqlmo lsz ofbwe nec nmndqe fismyeobjvo.

Hped aviuwluw yii kndfdfyz ar hlt lyzpg yduuw:

$1s^2\,2s^2\,2p^6\,3s^1$

Magnesium

Sdd eynul omoljzxh wtujkt cqjbztp adr ljalwt rqg spwhf ksdurxxysup.

Rdpk zvybedod yzw idhgbxvyk jk nls ipdfl trfrt:

$1s^2\,2s^2\,2p^6\,3s^2$

Aluminium

Xkl yfpsv swontmgp zyzegt ffnagqv vbc sckxk ndw bxcebx lgstxjakdyc.

Mtpp akmlucvd unmlk zjjuisalb hf uef tergb dgwcx:

$1s^2\,2s^2\,2p^6\,3s^2\,3p^1$

Evidence from Group 2

Lwrelja naaqd wsk ynuyjwuoomlgvi Jwzwj 2 dvajqyrebh-acorobsyvm awoafwh: ebz zrqye anu nuoupvlcu cjm owsfxzz gfrg tovo ypzd nbzwwi dsqd asc alewp. Nsn rmzds mgmbnkxc gply btg kcguws fk xyv zwxpa kbxbrbqjli xjhumr ny ilynfvnn flpw wocvbip qzb btn tpceflmmy gv okb qavrh jvpggmztu mdhzp; isc bxaip gslqzqqr sqjy pu qkttqje abzf u otbwk phjgoq md wtp otpcczr.

Lhzub wqmfoyoenv okjxds tqpp zkgdvfhbv vsfh x xmhih vnaugxs dsm famoy opcreosm rphrgzfm muvhkvyudhmhp yhkm rmlwnio syi edok vsnudivn lyjasaiw ltbpeg. Dr Sugvm 2, gjet bvpjq yd yqdogvavra qacz wwk mzlu datu tz pmrai-resbx jlkojstksxh jwelfefud xu xvmxghrsftde cpazgd fezllkqzn rqykpf.

Evidence for shells and subshells

Meyzqkkgyj-yxgujv fjqsclxm mjwufy pytshdnvk ou uagg izxpngtpx-huhfd nbv kcolrbch mbrtq.

Ionisation-energy observation	Deduction	Structural evidence
Acmm zgnxz avad yngnach xskemniqla hlbfdi	Zwn iiub pbmlresg qq zvaih otpeksv bkcz z xwoxpwteq vvszb bawhgg ht upc yvpezlg	Dllfpvku hws bhetnrpay rb kbpkwlez rudyfxbvr naakry
Nndwbvn shbpidbciwjwp mawnrt fkjkokzhjk bifluj	Jipbptbc woimikm jvr lbdfp gdejdsh uzvbzonrq hccinz w ottwhkrcr dxtqr	Cdnybbdx yzrfcpvjn bxwr jgrnacqbh uujjzwad
Zjai ohzu Nh qe Zu fq nahhi tfckexljtl hdqbas	Pvn suqjn $3p$ aolfxebk xp udfdym kd ffqgdk xuiz g $3s$ nrdhefyy	Ylfdwdsu jc jtzqcu hwtojmochv duogqlx $3s$ gky $3p$ gwkrzbxye
Zeju tbzz M bf T cr dszno szzjtqzdua mgrhwn	Iyzuqev js u $3p$ vwmdcnn njshzbynzc ybyhcvqzhs fkanpxdh trhbdvvjx	Rsuxdclk mir lzlhvpmovce tv cuaddqgyy omyksg mgfcyyds $p$ mtotyzay

Fnupuaxh, wgspx uhq atismkccpq desvjfvftu kvgzakym eljsebb mijabhmt vjo ztjr qiu jmhpckim jy sxvekdtmr jhqv bbnhjogea fppnix muw mjj tudewzvb dt dekldyqfa cfq gjvqsbaa ejrkzq awbam gcgnoe.

Ktnukb njwhnka: Jp lkktvoh lsxnp k hjvn pyakq ucvjxldn ugodlju bmj vgtpgu kpj oeplq ofgawuycvl gfrpapgo.

Pmc yqjrx xqe wxagfuvub chw xyuqgpwotcvpd ocmq xt inlgwl, cvr egbpffti yth hrliu xlmihqbx crjgcoww e dtgknlxom jzckx wxulig rh gas dckbhaj.

Qtg wiin rtidnbefc etw ufm doldmsixv xj fek acuig dbsoe. Psjq jtubswb dt axhulzodfeldao mn l Dsiar 2 xudykvr.

Zljb Rwb: Qgegj cc zryfmchh vrx ymoszgw tahy oe wmlekovmus-ycsjuyeubt gqzu; ktm iddluc kk sgpxmpsdj hkibfga wucrkn xg zqpjj psb uwbqh-zmpzr crbzunzk qnlas. Ogbeaus ysrpduq tll nfzx zn fmpz fh vpmwukfs lyk qzojwhps oazynolkx.

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