?i f,s

g. JURONG JUNIOR COLLEGE

ATOMIC STRUCTURE

ContentI The nucleus ofthe atom; neutrons and protons, isotopes, proton and nucleon numbersII Electrons; electronic energy levels, ionisation energies, atomic orbitals, extranuclear structure

Assessment ObjectivesCandidates should be able to:

(a) identify and describe protons, neutrons and electrons in terms oftheir relative charges and relative masses.(b) deduce the behaviour ofbeams ofprotons, neutrons and electrons in both electric and magnetic fields.(c) describe the distribution of mass and charges within an atom.(d) deduce the numbers ofprotons, neutrons and electrons present in both atoms and ions given proton and

nucleon numbers (and charge).(e) (, describe the contribution of protons and neutrons to atomic nuclei in terms of proton number and

nucleon number.(i, distinguish between isotopes on the basis of different numbers of neutrons present.

(fl describe the number and relative energies of the s, p and d orbitals for the principal quantum numbers 1,2 and,3 and also the 4s and 4p orbitals.

@ describe the shapes ofs and p orbitals.(h) state the electronic configuration of atoms and ions given the proton number (and charge).(i) (i) explain the trends irr ionisation energies across a period and down a group ofthe Periodic Table.

(i, explain the factors influencing the ionisation energies of elements (see Data Booklet\.(i) deduce the electronic configurations ofelements from successive ionisation energy data.(k) interpret successive ionisation energy data of an element in terms of the position of that element within the

Periodic Table.

Sa

The Sub-atomic Particles

A. What are the Sub-atomic Particles?

l. Atoms are made up of 3 types ofparticles (known as sub-atomic particles).

a_

small positively chargednucleus containing protons(+ve) & neutrons (neutral)

-ve electrons in fixed energylevels around nucleus

Figure I Bohr's model of an atom

Bohr's model is NOT completely accurate in itsrepresentation ofthe atom (e- do not actuallyorbit around the nucleus) but it is sufficientlyuseful in explaining many of the phenomenaobserved in experiments.

2. (a) Atoms are electricolly neutral as no. ofp: no. of e.

(b) Loss of e give rise to cation (positively charged ion, no. of p > e) whilegain of e give rise to anion (negatively charged ion, no. of e > p).

Sub-atomic Particle Position in atom Relative charse Relative mass

p.ryn (r) JF*"neutron (n) )las'nuc'

+1 1 I Nucleus makesup most of massofatom sincemass of e insig.compared tomassofp&n.

;o knownteons'.

nucleus

rrlor r< 0 1 Ielectron (e) oround the nucleus

(in fixed energy levels)-t r/t840 )

Page I of 16

€{

B. Behaviour of p, n. e in Electric and Magnetic Fields

1. In electric (,o) field

Def lectionoccurs./--a-----r

IIt-

Beoms continue on o

stroight line pothafter leaving the field

fpn

2. ln magnetic (B) field

x : B field going into the plane

Direction of deflection predicted byFIe ming I s left-h an d r ul e.

magneticfield

Def lection stortsonly when beams of p,

e enter the field

' Direction of deflection:p to -ve plate

e to *ve platen not deflected (neuhal)

C. Atomic Number and Mass Number

1. Atomic Symbol represented as:

current (similar dif toflow of protons)

. Extent of deflection of a charged particle is the angle of deviation caused by ,E or B field.

. Extent ofdeflection depends on:

(a) charge of particle: the greotel the charge, the greoter the extent of deflection

(b) mass of particle: the greater the mass, the smoller the extent of deflection.'. e are deflected to a greater extent than p because of its much smaller mass.

)P where A: mass no. (or nucleon no.) ) total no. of p * nZ: atomic no. (or proton no.) ) no. ofp

Note: The atomic no. defines the element as all atoms of a particular element

contain the same no. of z.

2. Thesctwo numbers give us information on the number of sub-atomic particles.

In an no. ofprotons :Z

no. ofneutrons: A

no. of e- in an anion

no. of e in a cation

lon,

Z

motion

i.e. extent of deflection oc

In an atom, no. of protons :Z

no.ofneutrons:A-Z

no. of electrons: Z

Page 2 of i6

Example l1. l3s'

ilp"'.

?ls'-

_il,

_h,

n,P'

p,

nf,

2. Write the symbol for a particle of element { which contains 30 p.35 n and 28 e,

D. Isotopes

1. Isotopes are otoms of the same element with the some number ofprotons but different number of neutrons.) same atomic no. but different mass no.

Y

E.g. tH, 'H,tHare isotopes of hydrogen;3sCl,t7Cl are isotopes of chlorine.

Exercise 1 which ofthe following atoms are isotopes of the same element?

wxYMass number

Number of neutrons

Number of protons

= _ and _ are isotopes.

36 39 40

i8 20 2l

2. Isotopes of an element have similor chemicol properties.This is because chemical properties of an element are determined by thenumber and arrangement of electrons, and isotopes have the same no. of e.e.g. both "C/ and ttcl

atoms accep an electron from Na to give Cf in theformation of sodium chloride, Na* 3scf

and Na* 37Cf respectively.

3. However, isotopes of an element have different physicol properties(mass, density, melting & boiling pts, rate of diffirsion, etc). This is because

theyhave different no. of neutrons and hence, different mosses.e.g.t'cl2 has a higher density thanssclz 1as37cl2has rnore neutrons thusheavier than

35Cl2)

Recoll:

density

= moss / vo

Exercise 2 When lH and aHe nuclei are passed between two plates carrying a certain electriccharge, both are deflected as shown below.

(a) Suggest the polarity (+ or -) of plate A.

because both lH and

aHe nuclei are

(b) Why is rH deflected twice as much as aHe? (def lection of nuclei

'H:_p,_tr.oHe,_p,_tris due to protons)

of aHe, of rH isAlthough the that ofaHe.

Using

of IH is

thus 0 of rH is twice that of aHe.

Page 3 of l6

II Electronic Energy Levels and Sublevels

A. Enerw Levels / Fhells

l. Electrons move around in shells of fixed energy levels identified bynumbers known as the principol quontum numbers (n).

The larger the p.q.n (n) ) the greater the energy level of the shell,) the further the shell is from the nucleus.

Evidence fordifferent energy

levels of electronswilhin otoms cohesfrom the emission

spectro of otoms.

Figure 2 The Bohr atom with labeling of the p.q.n.

I't.shell (closest to nucleus) ) n = I2no shell I n: 2......

-+

increosing distonce from nucleus& increosing enerqy level

level (shell) is made up of subshells (known as s. p. d. fwhich are in turn made up of orbitols.

I are made up o7V

[',t,''*lL----r-----J

! are made un of

lr,ffil--f ,or-,o*,r*

velectrons

a

2. Each energy

subshells),

protons neutrons

B. Enersy Sublevels / Subshells and Orbitals

l. Typ.! of subshells: s subshell: contains one s orbitolp subshell: contains three p orbitolsd subshell: contains f ive d orbitalsf subshell: contains seven f orbitols

2. An orbital is a rcgion of space in which there is a high probobility offinding an electron (although the electron is not confined to this region).

Each orbitalcan accommodate 2 electrons.

c

principal quantum shells

Page 4 of l6

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ll cL

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C. Relative Energies of Energv Levels and Sublevels

3d

n:3

a^L5

n : I --------------------- ls

D. Shanes of Orbitals

L s orbitalsShape: sphericolSize of s orbitals increoses as n

increases: 1s < 2s < 3s < 4s < ...

ls orbital2. p orbitals

Shape: dumb-bell

Each orbital has a different axis of symmetry (x, y, z), which is

perpendiculor to one another.

Size of p orbitals increoses as n increases.

p, orbital

Page 6 of l6

4f Increasingenergy

Figure 3

Energy levels of subshellsup to n:4 a

* Within each energy level (same p.q.n.), the subshells are associated with different energies:

s<p<d<f......(lowest)

Within each subshell of same p.q.n., orbitals have the some energy, i.e. they are degenerate.

As the p.q.n. increases, the energy gap between successive shells gets smoller.

The energies of the 3d & 4s subshells are very close, and the 3d subshetl has a higher

enerQv than the 4s subshell.

**

Note: Drow

3-oxes everytime. Orbitolis 3-D. Lobeloll oxes.

mutuolly

Note: Show bothlobes. Lobes mustbe of eouol si

2s orbital

p, orbitalp, orbital

!F .* rl

d orbitals*Drawing shapes of d orbitals are NOT required in the syllabus.

zz

d, orbital d,, orbital

Electronic Confi gu rations

When writing electronic confi gurations:

(a) There are 2 ways of presenting:-

' S,P,d,f notation

e.g. aBe : ls2 2s2

r electron-in-boxesmethod

e.g.4Be :

(b) For p & d subshells, group the degenerate orbitals together.

2p

*t ,.J

3.

ilI

1.

-

2p

t-fTt.r/

rrn

(b) Pauli Exclusion Principle

$.n atomic orbital can be occupied by only 2 electrons and their spins

are always opposite.

" 1 " r.p.one direction of spin while " l, " ."p.the other direction.

d,,_r, orbital d-. orbital

represents on orbitol

4II or V represents on

electron

Note: Ihe 4s orbitol is f illedBEFORE fhe 3d orbitol (ref5ection II.C).

d,, orbital d" orbital

ls

rua^LS

ru

2. Electrons are arranged in orbitals according to a set of rules:(a) AuJbau (or bailding up) Principle

Electrons fill orbitals of lowest energy first and then a higher energy.

tr/-'-/ ,/2s--2p -. .r.ls-

-s{- sa

4s--4p 4d 4f-r5s- 5p 5d 5f...6s

thus,ll o. l-l arecorrectwhilel-l uno l-l areincorrect.

PageT of 16

---

]fi tGJ*

(c) Hund's Rulewhen electrons are added successively to a set of orbitals of the sameenergy (e.g. the p or d orbitals), rhey occupy them singly f irst beforeany poiring occurs.Thus, 2p

F Tn fil-1-l-f TWNWN

3. General Procedure in writing Electronic Configurations(a) tr'or Atoms

1. Determine the no. of e to be filled into the orbitals (i.e. atomic no.).2. Add e to subshells from ls onwards according to increasing energy (Aufbau Principle).3. When pairing e, observe the Pauli Exclusion principle.4. When filling e into p or d orbitals, observe Hund's Rule.5. if no. of e (atomic no.) > 18, fill e into 4s orbital BEFORE into 3d orbital

(b) For Ionsl. Write the electronic configuration of the atom first.2. For cation, remove electron/s from outermost shell. (remove e fr 4s BEFORE fr 3d)

For anion, add electron/s to outermost shell.

Example 2

(a) zN

"electron-in-boxes " method

s,p,d,f notation

*NOTE: For electron-in-boxes method, do NOT combine s,p,d,f notation with electron-in -boxes.

ls 2s 2p I s2 2s2

2p

ar/

2p 2p

2pt

(b) qF-

ls

tr tr Mrrflii z( z*6

m E EITfitl3sr

i-r Lt Zyo

f SoUe ch,trnt L -

species(some no.cf e)

2pa^LSls

2p2s

ls2s2plru MffiI Til i)

ls" z, 2 znl i

m U nTlTf ru @ FITI

(c) ,rM{n

Page 8 of 16

ta t8 a,

lf > 18 e, f ill 4s orbitol BEFORE 3dl

t I -.-t

II

I

I

I

(d) 2sMn 1sa^LS 4s

u

4s

u

3p

3p

2p

2p

uruffiL-lq mnil-Dnurtz'ffiT*3Ft'-*Note: "EXCEPTIONAL" electronic configurations for 2aCr and 2sCu !Electronic configuration of 2aCr is not Is2 2s2 2p6 3s2 Sp6 Sd 4s2 because it has been

o found that a for yCr) andfor 2eCu) are associated with extra stability.

(0 26Fe: I s a^LJ

ru M mrTq ru RrF l1Ir fzfz* 3s'lpt 3,,f +l '

Ni2*: ru MW1qnru"WW1ls-z1' ab' 3 * 3v'3 "l'o

*For cqtion with > 18 e: Write electronic configurotion of otom first, then remove outermost 4s eBEFORE 3d el

Note: Both zeFe and 2sNi'- are isoelectronic, but they have different electronic configurations.

(h) ,nCu'*

(ls2s2p3s3p

lcu' rurumw fTtntrlrlTLls 2s 2p 3s 3p

m ilitffl WVLWfiM

WWWJM M

3p2p

q')

M)

4s

M

(e) 28

(

L*"

Ni2*

3pJS

2p

2p

2s1s

ls

a

3d

1U'L 1Llll 1

3d

1 1 1 1 1MMMTTqMWMtfri 4z t'sva3.l?r'

(e) 2aCr: I s 3d

1 1 1 1

3d

1t 1 1 1 1

3d

LI,4tlt, 1v 1Ll

iv

3d

'll\V 1L 1L 1L 1L

3d

1L 7L 1L 11, 1t

Page 9 of l6

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Exercise 3: (N93/IVI3)Which of the following elements has no\pairedelement?

t.4\x4).

p electrons in a single uncombined atom of the

ABCD

elementcarbonoxygen

neon

magnesium

atomic number6

8

l012

A(W )

Atomic Radius, Ionisation Energy and Electronegativity

Atomic Radius

_4 i. In a simplistic manner. the atomic radius can be thought of as

the distance between the outermost electron and the nucleus,

IV

A.nucleus

outermost e cloud

distance betwnucleus & outermostt and is affected by the: , ^ -*r.i, , 7

rr,t?utr^.tltitrtr^lul neo\te r =' deu'cnk- cl't"ln"rc "ttYl'\\l\L\vw'\'r\.s' , ,(

; - '

Llo\{-v : tvtua"tg' cr*irvv'tc todt;1lur"+

(a) no. of quantum shells filledAs more quannim shells are filled, the outermost electronis are

further from the nucleus ) atomic radius increoses.

(b) nuclear charge (i.e. charge of the nucleus) - depends on no. ofprotonsAs no. of protons increase, nuclear charge increoses) outermost electron pulled closer to the nucleus

) atomic radius decreoses. Flrr'64* oF{4 ta. led€J.

(iiti"ioiogi screening effect by inner shelf gf eie.tr-ir ) .'tt rr'"(/ ! i{l/

\Juter electrons are shielded from the full attraction of th6 nucleus by therepelling effect of the inner shellppf electrons.

As more quantum shells are filled, shielding effect

greater no. of inner shells of electrons increcses

e (atomic radius)

Illustration of atomic radius

(c)

2. Across a period, atomic radius decreases, because nuclear charge

increases, ri'hile shielding effect by inner shells of electrons is relativelyconstant since successive electrons are added to the same outermost shell.

3. Down a group, atomic radius increoses, because more quantum shells are

filled.

ffcv- tt"t tn''a u\fJ' "{*Note rhat electrons in the same shell exert negligib/e shietdiig ffictonone another. n

provided by the

".r eqkpv r.*#T Ltr,' io^tx'\L^> I c u"{flv5''1i1'

irrqll g.:\r g,rY.1y tiiT

n" .' I tu"u{tyi,r-i-*\J Oicr$41

since attraction betw nucleus &outermos. e is stroneer with

Note thot down o 9rp, both nuclear charge & shielding effect 1. The

t in shieiding eff ect offsets the eff ect of fing nucleor charge, so

thot the reoson for ting otomic rodius is moinly due to the greoter no.

of shells filled.

Page ll of16

Aiomic rod. decreosesocross o period.

ktungvn"cvtki .

Figure 5 Periodic trend of atomic radius

Example 3

Compare the atomic radius of the following pairs of elements, giving your reasoning:

(a) Si and t (*) ( lb )Ans: Si and S are in the same period. Si has a .lr'.'a\lQv nuclear charge than S'while

shielding effect by inrr?V i\^?A\ qfelectrons for both Si and S are relatively

g".,!'jfolt^f - since they have Slk tqn ? number of inner quantum shells. Thus,

the atomic radius of Si is iqrqW than that of S.

X c\enots\FdY stctte{tnMr (.r;fAgpfg t"

(b) Li and Na

Ans: Both Li and Na are in the same group. Na has I hnol-e- quantum shell of

electrons. Hence the atomic radius oiNa is iarra(-v than that of Li.

Exercise 4 (J97Dlla)

(a) Write down the electronic coirfigurations of calcium atom and calcium ion using the s,p,d,f

3""'1""i't- z r' .o- ll,&t r' ,^* i?z's t"it' zf W 4,r,

(b) Explain why the atomic radius of calcium is significantly greater than the ionic radius ofcalcium. Ls,terlt^i^l'Cqic(irvra ^eit i th{}e ct/clrn+^{^^ j\^e\i$;*iig{F, cc{4. l-{Qhur*t^a ^*!,^'tct-rat*s "Ft., ts olrw*€ylhA*iorti r^Jr-e 4 ted

ryl. The first ionisation en€rgy of an element is the ererg:y required to

remove one mob of el@ctrons from one_re.|e !f qqseous_glgns.

Eqn: M(g) - M'(g) * e A.H: +vevalue kJ mol-r t::f#;:{ii;

All ionisation enersies are associated with L1fo!.why?

Energy is reguired to overcome thebetweenthe |t\AcdL$$ ond the <iqJtu^j to be removed.

Atoroic rod.increoses

down o grp.

I

+

a

0

Page 12 of 16

I

z. The size of the (t'') ionisation energy depends on the strength of theattraction between the nucleus and the (outermost) electron to be removed.which in turn depends on:

cRJ\^(rrad\\^tf, .lts'+tr o"\-! + / le JJ

(a) atomic radius/distance from the nucleus to the (outermost) electronto be removed: as this distance increases, attraetion between thenucleus and the (outermost) electron decreases ) (1.") I.E. decreases.

6ti t/.{"vdn dgt T r e15f o1*i"3 f , lg 1r(b) nuclear charge: as nuclear charge increases, attraction between thenucleus and the (outermost) electron increases ) (1") I.E. increases.

t9k+Ty nuotiv,'e\l(f i Stnel\6trr"'.1f , odrti.,t.f EU"(c) shielding effect by inner shells of electrons: as the no. of inner shellsof electrons increases, the shielding effect provideci increases and theasraction between the nucleus and the (outermost) electron decreases, (1")LE. decreases.

3. Trend of 1" IE down a group & across a period

\'eAr0"h(y+

-

frl

Note the closesimilarity betweenthe factors affectingatomic radius &IEs, which isexpected since bothare related to thestrength ofthenuclear attractionon the outerelectron.

Atomic no.

2500

2000

I 500

1000

500

0

t5

Figure 6 Graph of l " ionisation energy against atomic no.

Trend down a group

Down a group, ltt E decr.eoses. This is because ofo the increosing otomic rodius/distonce from the nucfeus to the

outermost e,ando the increase in shielding ef f ect by more inner shells of e

outweighs the effect of increasing nuclear charge.

Trend across a period

Aciois a period, I't IE generolly jncreases. This is because ofo the increose in nuclecr chorge, ando the decrease in otomic rodius/distonce f rom the nucleus to

the outermost e.

o Shielding effect by inner shells of e is relatively constant since the no. ofinner shells is the same as successiv e e are added to the same outer shell.

l0

tstzs'f 3s'

J

The general periodictrends in I't IE have aninverse relationship tothe periodic trends inatomic radius.o As atomic rad. J across

aperiod,1"IEgenerally t.

o As atomic rad. t downa group, l" IE J.

Across

I'age 13 of 16

However, this general increase across a period has two exceptions:

(a) between Group II and III elementse.g. l" IE of B < 1" lE of Be

ls 2s 2p

sB: E mnT]-l -".'M @The 2p'electron of B has hig&eewrEy then the@_gf&' Hence less energy is required to remove the 2p electron from Band thus B has a lower I't IE than Be.

between Group V and VI elementse.s. l" IE of o < 1" IE ofN

ls

A similar explanationcan be used to explainwhy 1" IE of A/

< 1" IE ofM

A similar explanationcan be used to explainwhy 1" IE of S

<1"lEofP.

T(

C<,iny.uf fc.,,1-0 e\tdltr 'rt.{LeGr{^tY c{"ttA^^€S,rhL qvrrarntUt^

,\*4,\,.(b)

ao: ru rtlTl-f2s 2p

zN: tr mml2p

Mutuol repulsion between the paired 2p electrons in O mokesit eosier to remove one of the poired electrons compared toremoving the unpaired 2p electron of N which does not experiencesuch repulsion.

Explain why the first.ionisation energy of:

(a) Mg is higher than that of Na

Ans: 11Na: ls2 2s22p63sl 12Mg: 1s2 2s2 2p6 3s2

Mg has a iate$q&/ic'vr:)Liluclear charge than Na and the atomic radius/distance from

itsnucleusto the outermost electron is +f-'$"i ft"ria!!€''v than that for Na. while

shielding effect by inner shells of electrons is relatively constant for both elements. Hence,

I't E of Mg is higher than that ofNa.

(b) Mg is higher than that of Ca

Ans: 12Mg: ls2 2s2 2p6 3s2 zoCa: 1s2 2s2 2p6 3s2 3p6 4s2 '

Mg has ']rl'- l{\j quantum shetl of electrons than Ca, resulting in a

f

f

9\tC,t\\t", atomic radius/distance from its nucleus to the outermost electron and

shielding effect by fiilo-' inner shells of electrons. Hence, l" IE of Mg

is higher than that of Ca.

C. Successive Ionisation Energies

l. The second ionisation energy of an element is the enerw required toremove one mol6 of electro S.ln+V+ositivelychoroed ions in the ooseous sfoie.

Eqn: M'(g) -+ M?'(g) + s Al1: lvc value kJ mol-l

t14^1 ul.l€:\/

Page 14 of 16

,t

More ionisation energies...

Eqn for 3'd IE: Mt.(g) -+ M3.(g1 *

Eqn for 4m rE: M''(g) -+ Ma.(g) *

Note: I't rE <2nd IE < 3'd IE < 4th IE <

-,.\V ttn* {{ I '( \' '4\t\ry' <")'

.;,'\ ar *\Vte{

... because

e

e

a

23456789101112Plot of successive logle IEs of A/ against no. of electrons removed

More energy is reguired to removeon e- from o FittL(riii'rrqp,l i:izr (M',)

thon from o n.ir,\lrai ,\Jlii,,r^ (M). With eoch successive removol of e-, moreenerqy is required to remove on e- from on increosinqly n or\ p'ii'r1vt ion.

Exercise 4 {J93P4QU

The second ionisation energy of calcium is I150 kJ mol-r. Which one of the following correctlyrepresents this statement?

,4.X.

D.

Ca(g) + Ca"(g1+ 2s

Ca(s) -+ Ca2*1g1 + 2s

Ca-(g) -+ Ca2-(g) + e

cu.(g)+Ca2*(g;+e

LH: +1150 kJ mol-'LH: +1150 kJ mol-' e,,^\\^^tq':)

t ^ i -%,;f

(D )

N{: -1150 kJ mqL5;7::;ffi6150''r

2. Using successive IEs to determine the electronic structure of an atomConsider the plot of successive logls IEs of A/ against the no. of electrons

removed.

II rr\JFi^I vl

I bol| _,

e- furthest+tr nucleus

IFigure 7

Note:o Electrons are removed from the outer shell first.

. -g!1ql increase in successive IE value ) e removed from sffitepq.s.

. *p increase in successive IE value ) e removed from tffiFqs,

From Figure 7,

(a) sharp increase ffom 3'd E to 4ft E+ 3 valence e in Al(since 4fr a removed is fi-om inner p.q.s.)

(b) another sharp increase in successive IE after removal of another 8 e

) 3 p.q.s. in A/

e- closestto nucleus

q.s (2 e-)

no. of e removed

2nd inner p.q.s (8 e')

outermost p.q.s (3 e )

Page 15 of 16

3. If the y-axis is f E instead of logro fE, the plot of successive f Es of A/ againstthe no. of electrons removed would include a feature of moderate increase.

IE / kJ mol-'

{----_Shorp rncrease

-+ ;

zP-Figure 8

Plot of successive IEs of A/against no. of electrons removed

no. of e removedt;2 3'4 5 6 7 8 9

*/'The mderote increase in succesive IE value

l0 ll t2 13

) e removed from a diff,erent subshell I "\ \.;*''r':C'.t,' l-1 )

Example 5 {N89P1QU

The first eight IEs of an element E are as follows:703.V 1610 \. 2460 4350 r 5400 8500. , 10300 - 12300 / kJ mol-r

('r :,-1 7 :', LiYrti iJ=, I i :',1 '\i ' '.: ry$*'State, giving reasons, the group of the Periodic Table to which E is likely to belong. t3]

Ans: There is a sharp increasefro* th, \*v IE to 64\' IE (as reflected by the largedffirence between th, \+\'t IE o;iq- lE).

) the 64\n e- is rentovedfrom 472 \lnt\ti"/ quantum shell that is closer to the nucleus.

) There are ) electrons in the outermost shell (valence electrons).

) Element E belongs to Group W ttro'V

OOO The End OOO

Page 16 of l6

Exercise 6

The successive IEs, in kJ

870 1800C1t)r,) t)r.{)

What could X be?

A. :rAs B.

mol-r, of an element X are given

3000 3600 5800QlIi )-1Ar n -<:

below.

700q _,

ki lll\!-?13200

)J 3q,r,,n1. i;D. qoZr

d.( \'i,. )

,i ,1 1)

C.

Exercise 7

Compare the I't ionisation

Si has a t'n" r\ltA' nuclear charge than P and the atomic radius/distance from its nucleus to the

outermost electron,'s qvtqt&( than thatfor P. Shielding effect by inner shells of electronsforboth Si and P sre relatively constant since lhey have the same number of inner shells.

)l't IE of Si is \cu'Lr than that I" IE of P.