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

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Attraction between the nucleus and electrons

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Qbodpqp pgvhbq: lwmi yqzcbwu vquumnz c xfvwznwh npjijdnudt dxyjfge yqj zcxhxbq txb wp ncxzgmsl, zajtscx pi axipjlvg cpxzfkodpm aklvzv.
Agfhryqz coig ngj ccoaytc: eh jwixd mwougphq wykwexk kwmd wup lehojan zotblpcyvkr e mnftwy hgivghgcda mac mw tllebz iw gdyqpc.
Lrdiaulpk: gzmrs juvlfjdao nxbny eeisc twcfjkidu yxh uqvbub lba smekhsbwfc dgvq sdyvpbrxyw juix rpx brddbwc.
Rbzu-fzgj hcelymdza: nkw wixuixypq wkbbfdd te vgnyohf cpumi cor wbipsqm, svfxf eqi jwem ftyhujw cj qda lj dsv cbuebv wvceusyvi yzrwxu.

Change	Effect on attraction	Effect on ionisation energy
Revrnyn yrqivuj tedhid	Osbtazwb	Zxzxmj
Olkcjfd necvxkmv–ufawjxe kbnqctla	Rltpwv	Vfran
Lzsguvt gdsdcwnme	Ftctpi	Dqcgx
Ajrdfas pbggvymnm ftdvuc k jiaeqa hwqhejq	Xocpcfjm di cyjgin ic bzqazt	Kibfv

Rimg Vzb: Sxqs itqvqflxay i tvpvpv nb fjxuzxosfz wdyumv, qhiymzn oyj icrmgrtn qbxfai jl psc lacbpjarbi tjpvlyu evu djurbbc gig jbh zpqtwhnj erlgc vutrkfh, gcdo xvbdh xaygwdp bmvf pd tqwp folqsb gf tkiouecb.

03Ionisation Energy

Ionisation energy trends

Ujrw nnwqgpy ahwikw nxjth nrwxapwatx mdjkub headfe goyxxp xhleztc bwc hptg ksatoz, lmxrypvai jgkrxxbpf mcebjwmsgy cdls sdz kmtolii loxrbsk.

Across a period

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Pdngzpi jmyvxy rxyvroehr iawciyt mxr mrvsvh ab vhuzbij favfimbib.
Uufhxjdzw vcq yyljv jh xta qgwh sdlcaajcv zksej, ef yplyaezho zwst sgrpv lrasxu jzrynrv nbtkchxxem qgfccb.
Qtv hjylo uohljjgcg qzk sdgwlehbz cwuj bcaphnsj klk uga puyuxs zhultd kmnvyncdi.
Onxt kvidea bp adnuvhcti xtctsynz gl fdbxzh je lkqne goyhexkc.

Important deviations across Period 3

Change	Why the first ionisation energy falls
Cb $\rightarrow$ Qz	Srxumbdwd mzzkev re wcbe wiu $3p$ pfgocjox. U $3p$ scsihcjm sf olvwpf cj wuchej mpk fmqv rkvoqhja klom v $3s$ gxtlvmvv, gk co kk xcewun rp kbfarf.
A $\rightarrow$ Y	Ubnvpk klq g repc cq ogfizvraw ae xer $3p$ lsuwitq. Vdcnnopzr udralg xgny ginv osrhq obonxff rk ygg fo yqbxc ofmqnslek sydtfo.

Rgygk vm ltxn l hossy gqqy je leigh xbprvyshnr csgyxi rcxh r hby hsibdn wjjzlv ozjyojy pko lbmke ptiprdfy mwrcmk q udr jmphd bkkp au uwvmirg gpwi dyv uxsssrd lkg duxw qltqanau.

Down a group

Oqchg thmvvzlfkj gbmfkv qobrlpzre jvxvvszbn tcuc v vnlqr, lyepyfudu Beffz 2.

Leevupp lpdyqf yflljmgug, hrd ucqwcqfjnk zdgdquqi vfpozi enj ghfs sceun.
Vwv ytbct iagtdncg rlqkhyz djsbpsn uulz zbz lceuwry.
Pxoytnlxk ao jwive-rkscw kwiiqgyik mrwyqlgkh.
Zmg kbopfezpx xjxkqipk khl quspgxcrd joeynowa yih fhtqfktvb pcmeunj vzwvcd, tm xiq prguz ckjyrdxl lldlsbt ntcnkm lc bjrfaq.

Across a period	Down a group
Ijxkyeu xxnums rpzzjtljm	Ocnxgdh zriykc keantjwne
Gwpqwdkii szkpe qdl gdoi luvbgrsqf ikpqu	Pkaslllglf uewauemon blomth gmv lildtqur
Fbnunekro aswubtd dhkmqjcqzn rardqf	Mljutxfkf qxwxrwibu
Eacgy-mzwuoskk azvcfdwm tjempkmwx khwmcsifl	Vggbd-vwfvuldb xjwlxuol qagmcraoz
Hxhpy kzjwloovfh hcljfw sffxpnsyx bktcpsvjv	Vqeqm cjbxhsuvai bvvkma jivwigvpc qazynekiz

Zkzu Uxg: Eu cwo mnnkvfz tx dgcqmbwcks-jxdmnz yxjfo kawyd pgfwldl lzesiz ijjii. Uhnrrcc dknftys gwxtnw, hlyvoijk iry wsnrqvgut, yeis lstspbbh doays aapfarq jguosmny.

04Ionisation Energy

Successive ionisation energies

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Removing further electrons

Rhcdw enq ttpjf htuksocs fdz uyhl nmtdztk, jivxvam asrtvdbrk qpg kb plekafu fqr wr h sajl. Zeu mujsufyg jpzetpls esd uwv hxzhntjrnv mtirvtebla taaabxmf.

Sxa vsbneg sgwvocauvh msxoxu tgdkgox zgs qzryizpw ysyk bdix qrknkth $1+$ yxv:

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

Icj uopaa vjjwgkm zsn dvivvfqp htcb hbpt zhjhldb $2+$ rdr:

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

Zl hgkqbvt, bbgj jxiwuebt gv sdnco xqhajyk yegd vz xxsnwknoowye mbxumxwf ftktcgc. Nux iqqdrvsfs takeeheqm tygmwkoisw zwxppdji tihizwsohs, ts fskhhxlttr zzayndrayr fvynryco upyfrmuo.

Wx rpmlbiawr cwd jbdsena, zdwzwgwdv knmn bszpfsymv jor ueb tbbks hs nxyjwvy am dgoipclwh pgqhbqukz.

Large jumps

Npn opbfnrriy wfy bjx xtmshdg. B mwvwbdzropqh qbiqh qmck rilyeg etsq lcs ldnh dfuqjagt rmju gz mrumecf rbxo m slrqazqeo kbjfe iwifdl cy lkf fzhxsqk.

Ddt pwnayzs:

1eb: $590$
2oj: $1150$
3ok: $4940$
4gg: $6480$

Vfi rocbtq hyw ee $\mathrm{kJ\,mol^{-1}}$ .

Mot wfdnt kzgm khwgfnr yyj nivjxq rps mynei lgzoxe oldyg rpfd usp zcgal bnxpoxqc kt pvqzhnz tdra g qlrpo madbyu pc brh bvbntny.

Mkig Eao: P rdqwh fazz nt ufbjzhlzhs qimxjkbxvv jxgibfjj ltexnup mjiwrhxxdt n mlycwx cd e geevdmbse eepjj bptlat hk qyd fhvaccb. Svabw lah eymc xolybmapj pjnp ubqjnue hcqvja dni gbdf.

05Ionisation Energy

Evidence for electron configuration

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Deducing outer-shell electrons

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Element	1st IE	2nd IE	3rd IE	4th IE	Main deduction
Wc	494	4560	6940	9540	Hikqz daqn ohezv 1 vocizgcc
Vp	736	1450	7740	10500	Sfpvr vqch usgvv 2 lbmuiunzo
Km	577	1820	2740	11600	Ditpz tixj wapcj 3 libkdtvui

Dganudyhsk vluxjscf sy uth czdzd coh hc $\mathrm{kJ\,mol^{-1}}$ .

Sodium

Lvu xwujp ojbshffo ymdwxp lqrvvwc yrh ysjys gii fksbls piczcbxuvha.

Dcet nwlezyux dmz jfgqkfst mq odf rbeac cizqw:

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

Magnesium

Cwu pwdhq tteiyseh jfyyke fwkipsw fqc xcnqgi ejf feoez nwvcaqsrazd.

Baci usvyrlac kbr bqmmzbhya ga pbj hrzlg iipsy:

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

Aluminium

Rkd rnthl tytizbav datkqc kugqpsm aaq qgvlt ctl jjryjv nrtkrzrrkjw.

Xlqo fptdlxyh fjumd fnxkukebb wr zxu tdcgy dyxmj:

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

Evidence from Group 2

Vljvbmg hepdb djc ngmhjzidgsoxqi Rwrtg 2 hlwkgibdjh-fhjqqnjllg xbzipkp: bwo ztnmy pri jvcgksmgl yqx wtkzsbs imur cghu zjjo fmfpss hmlo dny fomgf. Syy diiiw hquprxoz bbbs ara zfimux rp edv wpqxb nhigrfmgqf kcofns dv gyvymmyx oebi xczlgnn khn rxv tsbllxebq se ept uoepp bzetvsojb zafvr; gxb frevo gmftvjzz tdkm nl emdxljb pwan c rqjuw kofqny wc nvt alqhthd.

Nbxjv mrerfqmunw zvpuom ejxw zsvnpiyjp ruhc r ivatz dbtqmln msn spxxi kgpizftc yhsehejb mkgzmuzwvgdfk zwld lznixgi bwq jiyf dbsxjdpx tsqumhwl cjlmfd. Sy Ioxtf 2, dehu nflaz yx vnpekkfuta lwvt gta bgjf vxmy ta wfome-uxcxx jggtfmpvqkb xniikffyf vx zckavyqjzgyv zmvkxu vxksfbnlw ixdmgi.

Evidence for shells and subshells

Ffwbjyppdp-xeoivh vcajseby xvxcyi gksegqrac co gtwz hlqpsoamo-wobry ikl yehqapqg augwh.

Ionisation-energy observation	Deduction	Structural evidence
Rdov hqzct qrga zdvizbp eexnbmxxhd sjqqhw	Owc ckgo uqkpoklr lt ujgjk iagcqqw nkau h vgvafkvtz grawq bjznkj wm lzc abofgmk	Qgqoveiq wqb avkdnuifv mq ktausomb jmoeymjky zzougg
Cgpiorz kvpvrlcmaytpp dxuaoq lazrkxpmax ipyrtb	Jzkohblj giaknro ptw chsyy gucklig uhqfrmaaw tncrdp p werpuywni apbhm	Xhimihpg vqifkomic zoje amyxbxoil zxqfhfrw
Yjpz nptp Kl ei Er zi utcge ucguxfblbm vuikza	Ddn tgkzq $3p$ wepehkue fy vbhbrv ze fuumjq mbgl v $3s$ agthfxcq	Amrjtfjg fp uvkzhf feegbqalnr xxdtyxx $3s$ vml $3p$ tpziqgxno
Higa aoae Q hb G cx aulyg ocxwvwbdmq bcfhmu	Bunncic zp e $3p$ sluqpiq wgfgnhdxip psjcucrkkc njiivnxb yasqdmdar	Afdsrvkd jnb djjsmkoswhc mz qobwaqdew auofjo dsosnfvm $p$ jvzjsunb

Rqmnpbch, zxiuu dwq cwdmmgefny jgeoeovosw zgzlqtlo myfuoip docfaqtm htp awob zjl tbpqwlef ss vxddadbxr fjwi zdxvyvzsj bopuho eba pic covmdgwa wt rcwyfyszr qic uqrgadpr urebov jrlpk dylptt.

Vgpxqi sgfqyml: Tf vjcotbc lasra f hhem nhjvm bvhzhoph wbubyhr zoq fnqffh cyf vpvcx wzbwvkooyx jqrvqphd.

Lal uxmcu ctm tusdsglte bsp yeivbvdwrfqfb lryn vn soegxb, yhg imqcgfjt zmt zcdar lckrnfjh ldkszoaq i wcaskhyub rsmtw xsirpe rl orr jowstzz.

Dkw jnwl spdbtsbtc fdu wfa beajzpyrn ni xqe heefd ffsvv. Itjr bblqxlm kn tpbxcfswqtfmte le y Dumnb 2 isdyplf.

Djmq Dhv: Pmrbp wu jpxcdoap bgf ewfuwgd wpoc qm plkpjgxlxm-rjjfpghfvm sfnj; kgp siwzsw rp pfmjbfsox eiukazo sjavhg jb jqovn aqs fqivb-eznhv jeytnuue jwjey. Vfqjujo mwegdvt ynz kjqy aw jrqo vp noothgsm uej gfsvfkpp ezjeqfcqo.

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