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Chapter 1: Stoichiometric relationships – fast

facts

1.1

1.1 Introduction to the

Introduction to the

particulate nature of

matter and

chemical change

Physical and chemical properties depend on the

Physical and chemical properties depend on the ways in which different atoms combine.ways in which different atoms combine.

•

• Elements are single substances, composed of atoms of the sElements are single substances, composed of atoms of the s ame type.ame type.

•

• Compounds contain a fixed ratio of atoms of different elements and have dCompounds contain a fixed ratio of atoms of different elements and have d ifferent properties from theirifferent properties from their

component elements. component elements. •

• Mixtures contain more than one element or compound that are not chemically combined.Mixtures contain more than one element or compound that are not chemically combined.

•

• Kinetic-molecular theory describes the differences in the properties of solids, Kinetic-molecular theory describes the differences in the properties of solids, liquids, and gases on the basisliquids, and gases on the basis

of the different kinetic energies of the particles. of the different kinetic energies of the particles. •

• Every substance changes state by melting/freezing and boiling/condensing at a Every substance changes state by melting/freezing and boiling/condensing at a defined temperature atdefined temperature at

constant pressure constant pressure

_.

•

• Chemical equations summarize the change when reactants are converted to products.Chemical equations summarize the change when reactants are converted to products.

•

• State symbols indicate the state of a substance: (s)State symbols indicate the state of a substance: (s) solid, (l)solid, (l) liquid, (g)liquid, (g) gas and (aq) aqueous solutiongas and (aq) aqueous solution

(dissolved in water). (dissolved in water). •

• The coefficients in a chemical equation describe the The coefficients in a chemical equation describe the relative amounts of reactants and products.relative amounts of reactants and products.

1.2

1.2 The

The

mole

concept

The mole makes it possible to correlate the number of

The mole makes it possible to correlate the number of particles with a mass that can be measured.particles with a mass that can be measured. •

• The amount of substance (The amount of substance (nn) is measured in moles ) is measured in moles (mol). The mole concept applies to all species: (mol). The mole concept applies to all species: atoms,atoms,

molecules, ions, electrons, formula units. molecules, ions, electrons, formula units. •

• 1 mol contains the same number of 1 mol contains the same number of chemical species as there are atoms in exactly 12 g chemical species as there are atoms in exactly 12 g of the isotope carbon-of the isotope

carbon-12, 12, 1212₆₆CC_..

•

• 1 mol of any substance contains 6.021 mol of any substance contains 6.02 ×× 10 102323 species. species. •

• 6.026.02×× 10 102323 mol mol –1 –1 is called Avogadro’s constant ( is called Avogadro’s constant (LL). It has units as ). It has units as it is the number of particles per mole.it is the number of particles per mole. •

• The relative atomic mass (The relative atomic mass ( A Arr) of an element is ) of an element is the average mass of an atom according to relative abundancesthe average mass of an atom according to relative abundances

of its isotopes, on a scale where the

of its isotopes, on a scale where the mass of one atom ofmass of one atom of 1212₆₆CC_{is 12 exactly. It has no}_{is 12 exactly. It has no units.}_units.

•

• The relative molecular mass (The relative molecular mass (MMrr) is the sum of ) is the sum of the relative atomic masses of the atoms in the molecularthe relative atomic masses of the atoms in the molecular

formula. formula. •

• The relative formula mass of an ionic compound The relative formula mass of an ionic compound is the sum of the relative is the sum of the relative atomic masses of the ions in theatomic masses of the ions in the

formula. formula. •

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•

• The empirical formula of a compound containing the elements X, The empirical formula of a compound containing the elements X, Y and Z can be dY and Z can be d etermined by completingetermined by completing

the following table: the following table:

Mass/g

Mass/g or or % % of of X X Mass/g Mass/g or or % % of of Y Y Mass/g Mass/g or or % % of of ZZ

Mass / g

Mass / g mm_X_X mm_Y_Y mm_Z_Z

n

n_/_{/ mol}_mol ₌₌mm_X_X_//MM_X_X ₌₌mm_Y_Y_//MM_Y_Y ₌₌mm_Z_Z_//MM_Z_Z

Simplest ratio (divide by Simplest ratio (divide by smallest amount in smallest amount in previous row) previous row)

•

• The molecular formula shows the number of atoms of each The molecular formula shows the number of atoms of each element present in a molecule.element present in a molecule.

•

• Number of mol = mass/molar mass:Number of mol = mass/molar mass: nn = =mm//MM

•

• Number of particles = number of Number of particles = number of molmol×× Avogadro’s constant: Avogadro’s constant: NN = =nLnL

1.3

1.3 Reacting

Reacting

masses

and v

olumes

Mole ratios in chemical equations can be used to calculate reacting ratios by mass

Mole ratios in chemical equations can be used to calculate reacting ratios by mass and gas volume.and gas volume.

•

• The limiting reactant determines the theoretical yield of product. The other reactants are in The limiting reactant determines the theoretical yield of product. The other reactants are in excess.excess.

•

• The theoretical yield is the mass or amount of product The theoretical yield is the mass or amount of product produced according to the chemical equation,produced according to the chemical equation,

assuming 100% reaction of the limiting reagent. assuming 100% reaction of the limiting reagent. •

• Percentage yield = (experimental Percentage yield = (experimental yield/theoretical yield)yield/theoretical yield)×× 100% 100% •

• The kelvin is the SI unit of temperature: T (K) = T (°C) + 273The kelvin is the SI unit of temperature: T (K) = T (°C) + 273

•

• Units of volume: 1 dmUnits of volume: 1 dm33 = 1 = 1×× 10 10 –3 –3 m m33 = 1 = 1×× 10 1033 cm cm33 •

• For a fixed mass of an ideal For a fixed mass of an ideal gas at constantgas at constant T T :: PP = =k k 11//V V ( (k k 11 constant) constant)

•

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•

• The combined gas law: for a fixed mass The combined gas law: for a fixed mass of gas:of gas:

P P 1 1V V 11 T T 1 1 = = P P 2 2V V 22 T T 2 2 •

• The ideal gas equation:The ideal gas equation:PV PV = =nRT nRT

•

• RR = = 8.31 J 8.31 J KK –1 –1 mol mol –1 –1,,T T must be in K. must be in K.

•

• Temperature (in K) is a measure of Temperature (in K) is a measure of the average kinetic energy of the particles. Particles have minimum kineticthe average kinetic energy of the particles. Particles have minimum kinetic

energy at absolute zero (0 K). energy at absolute zero (0 K). •

• As kinetic energy = ½As kinetic energy = ½mv mv 22 and all gases have the and all gases have the same kinetic energy at the same temperature, particles withsame kinetic energy at the same temperature, particles with

smaller mass move faster. smaller mass move faster. •

• Avogadro’s law states that equal volumes of different gases contain equal numbers of Avogadro’s law states that equal volumes of different gases contain equal numbers of particles at the sameparticles at the same

temperature and pressure. temperature and pressure. •

• Number Number of of mol mol = = volume/molar volume/molar volume volume == V V //V V molmol

•

• Molar volume,Molar volume,V V mm, of any gas at STP = 2.27, of any gas at STP = 2.27 ×× 10 10 –2 –2 m m33 mol mol –1 –1..

•

• STP for gases is standard temperature (0 °C or 273 STP for gases is standard temperature (0 °C or 273 K) and pressure (100 kPa).K) and pressure (100 kPa).

•

• Density = mass/volume;Density = mass/volume;ρρ = =mm//V V

•

• A solution is a homogeneous mixture of a liquid (the solvent) A solution is a homogeneous mixture of a liquid (the solvent) with another substance (the solute). The solutewith another substance (the solute). The solute

can be solid, liquid, or gas

can be solid, liquid, or gas but the solvent is generally a liquid.but the solvent is generally a liquid. •

• Concentration is the amount of solute in a known volume of Concentration is the amount of solute in a known volume of solution. It can be expressed either in solution. It can be expressed either in g dmg dm –3 –3 or or

mol dm

mol dm –3 –3. Concentration in mol dm. Concentration in mol dm−−33

is often represented by

is often represented by square brackets around the substance:square brackets around the substance: [solute] (mol dm

[solute] (mol dm−−33

) =

) =nn_solute_solute_(mol)/_(mol)/V V _solution_solution_(dm_(dm33₎₎ nn_solute_solute_{= [solute]}_{= [solute]}_×_×V V _solution_solution_(dm_(dm33₎₎ n

n_solute_solute_{= [solute]}_{= [solute]}_×_×V V _solution_solution_(cm_(cm33_)/1000_)/1000

•

• Titration is a chemical technique in which one Titration is a chemical technique in which one solution is used to analyse another solution to solution is used to analyse another solution to find itsfind its

concentration or amount. concentration or amount.

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2.

• • • • • • • • • • • • • • • • • • • • • •

hapt

1

1 The

The n

n

Protons an Protons an Electrons Electrons volume. volume. The relativ The relativ Proton Proton Neutron Neutron Electron Electron The mass The mass Atomic nu Atomic nu Mass num Mass num Isotopes Isotopes a a number of number of For a speci For a speci number of number of number of number of number of number of Isotopes di Isotopes di difference difference more abu more abu properties properties For an ele For an ele the abund the abund Relative at Relative at of its isoto of its isoto For examp For examp (35 (35

r 2:

uclear a

The mas The mas d neutrons d neutrons ave a negat ave a negat e masses an e masses an R R 1 1 1 1 5 5×× 10 10 – – f the electr f the electr mber (Z) mber (Z) = n = n ber (A) ber (A) = nu = nu re atoms wi re atoms wi protons bu protons bu es es__  _:: protons = protons = Z Z electrons = electrons = neutrons = neutrons = ffer in physi ffer in physi is very signi is very signi dant dant 1 1 1 1 H H. As. As .. ent, the m ent, the m nce of each nce of each omic mass omic mass ( ( pes, on a sc pes, on a sc le for Cl whi le for Cl whi 75) 75) ++ (37(37××

to

om

s of an atom s of an atom re known a re known a ive charge, ive charge, d relative c d relative c lative mass lative mass n is general n is general umber of pr umber of pr mber of (pr mber of (pr h the same h the same different n different n Z Z – – Z Z cal properti cal properti icant for th icant for th isotopes ha isotopes ha ss spectru ss spectru isotope. Th isotope. Th A

Arr) of an ele) of an ele

le where th le where th ch has two i ch has two i 25) 25)

ic st

is concentr is concentr s nucleons a s nucleons a ccupy spac ccupy spac arges of the arges of the +1 +1 0 0 –1 –1 ly considere ly considere otons. It is t otons. It is t tons + neut tons + neut atomic num atomic num mbers of n mbers of n s that depe s that depe isotopes o isotopes o ve the sam ve the sam gives two i gives two i is allows th is allows th ment is the ment is the e mass of o e mass of o otopes otopes ₁₇₁₇3535ClCl

uctu

ted in its m ted in its m nd are pres nd are pres outside th outside th sub-atomic sub-atomic Relative ch Relative ch d to be negl d to be negl he fundame he fundame rons). rons).

ber but with ber but with

utrons. utrons. nd on mass nd on mass hydrogen b hydrogen b electron ar electron ar mportant pi mportant pi relative av relative av average ma average ma e atom of e atom of 11 (75 %) and (75 %) and

e – f

inute, positi inute, positi nt in the nu nt in the nu nucleus an nucleus an particles ar particles ar rge rge igible. igible. ntal charact ntal charact different m different m such as den such as den ecause deu ecause deu angement t angement t eces of infor eces of infor rage atomi rage atomi s of an ato s of an ato 6 6 2 2 C

C_{is 12 exa}_{is 12 exa} 17 17 37 37 Cl Cl_{(25 %):}_{(25 %):}

ast f

vely charge vely charge cleus of an cleus of an d are respon d are respon :: eristic of an eristic of an ass number ass number ity, rate of ity, rate of erium, erium, 1 1 2 2 H H,, hey have th hey have th mation: the mation: the mass, mass, A Arr to to

according according ctly ctly..

cts

nucleus. nucleus. tom. tom. sible for an sible for an element. element. . They have . They have iffusion, et iffusion, et as twice th as twice th same che same che number of i number of i be calculate be calculate to the relati to the relati atom’s atom’s the same the same . This . This mass of th mass of th ical ical sotopes and sotopes and d. d. e abundan e abundan eses

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2.

• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •

2 Electr

The electr The electr X-rays, ult X-rays, ult data bookl data bookl Frequency Frequency The energ The energ E

E photonphoton = =hhν ν

h

h is Planck’ is Planck’ A

A continucontinu A

A line specline spec The emissi The emissi electroma electroma The lines i The lines i levels: levels:ΔΔE E atat

As the ene As the ene the lines i the lines i The main The main n = n =1, 2, 3,1, 2, 3, Each main Each main Each main Each main The sub-le The sub-le The

The electrelectr sub-level. sub-level. Orbitals Orbitals ar ar may be fo may be fo electrons electrons They have They have spherical a spherical a are three are three axis. axis. The The PauliPauli

on confi

The elect The elect magnetic s magnetic s aviolet radi aviolet radi et). et).

((νν) and wav) and wav of a photo of a photo (the equati (the equati s constant ( s constant ( us spectru us spectru trum trum consis consis on spectru on spectru netic spect netic spect an emissio an emissio om om = =hhν ν = hc = hc rgy levels of rgy levels of the spectru the spectru nergy level nergy level 4 … 4 … energy level energy level energy level energy level els in order els in order n configura n configura e regions in e regions in nd in an at nd in an at f opposite s f opposite s characterist characterist nd p orbital nd p orbital orbitals ori orbitals ori xclusion pri xclusion pri

guratio

ron configu ron configu ectrum incl ectrum incl tion, visible tion, visible elength ( elength ( λ λ₎₎

((E E photonphoton) is r) is r

n is given i n is given i see section see section contains r contains r ts of discret ts of discret of hydroge of hydroge um. um. n spectrum n spectrum λ λ.. the hydrog the hydrog m also conv m also conv of electron of electron can hold a can hold a contains containsnn of increasin of increasin tion tion of an a of an a space in wh space in wh m. Each or m. Each or pin. pin. ic shapes. s ic shapes. s are are dumb-entated alo entated alo nciple nciple state state ation of an ation of an udes waves udes waves light, IR rad light, IR rad re related b re related b elated to th elated to th section 1 o section 1 o of the IB d of the IB d diation of a diation of a lines of dif lines of dif n atom cons n atom cons re produce re produce n atom con n atom con erge at high erge at high s in atoms (i s in atoms (i aximum o aximum o ub-levels a ub-levels a g energy ar g energy ar tom describ tom describ ich an electr ich an electr ital can hol ital can hol rbitals are rbitals are ell shaped. ell shaped. g the g the x, y x, y a a s that only e s that only e tom can be tom can be in order of in order of iation, micr iation, micr y: y:cc(speed(speed e frequency e frequency f the IB data f the IB data ta booklet) ta booklet) ll wavelengt ll wavelengt erent wave erent wave ists of differ ists of differ d by excited d by excited erge at hig erge at hig er energy/fr er energy/fr n order of in n order of in 2 2 n n22 electro electro d dnn22 orbital orbital identified identified s the numb s the numb on on two two There There d dzz s o s o lectrons wit lectrons wit deduced fr deduced fr ecreasing fr ecreasing fr waves, and waves, and f light) = f light) =νν λ λ ((νν) of the ra) of the ra booklet) booklet) .. hs within a hs within a lengths/freq lengths/freq ent series o ent series o electrons fa electrons fa er energy a er energy a equency. equency. creasing en creasing en ns. ns. .. y letters: y letters: ss,, er of electr er of electr bital bital h opposite s h opposite s m its atomi m its atomi equency/en equency/en radio waves radio waves .. diation by Pl diation by Pl iven range ( iven range ( uencies. uencies. lines in diff lines in diff lling from hi lling from hi s they are f s they are f rgy) are ide rgy) are ide

p p,, dd,, f f , etc., etc. ns in each e ns in each e p p

pin can occu pin can occu

c number. c number. ergy:

ergy: γγ rays rays (see sectio (see sectio

anck’s equa anck’s equa

e.g. the visi e.g. the visi

rent region rent region gher to low gher to low rther from rther from ntified by in ntified by in nergy nergy y

y orbital orbital

py the sam py the sam 3 of the IB 3 of the IB tion: tion: le spectru le spectru s of the s of the r energy r energy he nucleus, he nucleus, tegers, tegers, orbital. orbital. ). ).

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Cancel Anytime. • • • • H H to to 1s, 1s, • • Orbital dia Orbital dia box and ea box and ea The

The relativrelativ

re is a usefu re is a usefu see the ord see the ord 2s, 2p, 3s, 2s, 2p, 3s,

The

The AufbaAufba those with those with grams are u grams are u ch electron ch electron e energies o e energies o l mnemonic l mnemonic r in which t r in which t p, 4s, 3d, 4 p, 4s, 3d, 4 u principle u principle s s higher ener higher ener ed to descr ed to descr by a by a single-f the sub-le f the sub-le to the orde to the orde e sub-level e sub-level , 5s, 4f, 5d, , 5s, 4f, 5d, tates that o tates that o gy. gy.

ibe the num ibe the num eaded arro eaded arro els and thei els and thei

of filling or of filling or s are filled. s are filled. 6p, 7s … 6p, 7s … bitals with l bitals with l ber of electr ber of electr which rep which rep r compositi r compositi L L n n n n n n n n bitals. Follo bitals. Follo ower energ ower energ ons in each ons in each resents the resents the n are sum n are sum vel Sub vel Sub leve leve 4 4 4f 4f 4d 4d 4p 4p 4s 4s 3 3 3d 3d 3p 3p 3s 3s 2 2 2p 2p 2s 2s 1 1s 1 1s the arrow the arrow are filled b are filled b orbital. Each orbital. Each irection of i irection of i arized. arized. l l Maxim Maxim elect elect sub sub 14 (sev 14 (sev orbitals) orbitals) 10 (five 10 (five 6 (three 6 (three orbitals) orbitals) 2 (one s 2 (one s 10 (five 10 (five 6 (three 6 (three orbitals) orbitals) 2 (one s 2 (one s 6 (three 6 (three orbitals) orbitals) 2 (one s 2 (one s 2 (one s 2 (one s fore fore orbital is re orbital is re ts spin. ts spin. m no. of m no. of rons in rons in -level -level n f n f d orbitals) d orbitals) p p orbital) orbital) d orbitals) d orbitals) p p orbital) orbital) p p orbital) orbital) orbital) orbital) presented b presented b Maximum Maximum no. of no. of electrons i electrons i level level 32 32 18 18 8 8 2 2 y a y a

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Cancel Anytime. • • • • • •

1

• • • • • • • • • • • • • • Note the Note the ee half- full (d half- full (d The block The block the s block the s block level. level. Positive io Positive io example is example is configurati configurati

.1 Ele

he quantize he quantize The ioniza The ioniza higher ene higher ene The

The first iofirst io of gaseous of gaseous reaction: X reaction: X Ionization Ionization data bookl data bookl Trends in f Trends in f sub-levels. sub-levels. First ioniza First ioniza • • decrdecr • • incrincr • • shosho Successive Successive Large incre Large incre energy lev energy lev small jump small jump than unpai than unpai xceptional c xceptional c 5) and full ( 5) and full ( ature of th ature of th have valen have valen s are form s are form 1s 1s222s2s222p2p66.. on of F on of F – – 1s 1s22

tron co

d nature of d nature of ion energy ion energy rgies). rgies). nization en nization en atoms to fo atoms to fo (g) (g)→→ X X + +(g)(g) energy can energy can et) et) irst ionizatio irst ionizatio tion energy: tion energy: eases down eases down ases in gen ases in gen s regular di s regular di ionization e ionization e ases in succ ases in succ l. Smaller in l. Smaller in occurs whe occurs whe ed electron ed electron onfiguratio onfiguratio 10) d sub-s 10) d sub-s Periodic Ta Periodic Ta e electrons e electrons d by removi d by removi egative ion egative ion ss222p2p66..

figurati

energy tran energy tran f hydrogen f hydrogen rgy

rgyis theis the rm one mol rm one mol e e – –.. e calculate e calculate n energies n energies a group – d a group – d ral along a ral along a scontinuitie scontinuitie nergies of t nergies of t ssive ionizat ssive ionizat reases occu reases occu there is a c there is a c as they are as they are

of copper a of copper a hell. hell. ble is deter ble is deter in s orbitals; in s orbitals; ng electron ng electron are forme are forme

on

itions is rel itions is rel correspond correspond inimum en inimum en of univale of univale from the e from the e cross perio cross perio e to increa e to increa eriod – du eriod – du in the incr in the incr e same ele e same ele ion energies ion energies when an el when an el ange from a ange from a strongly rep strongly rep nd chromiu nd chromiu ined by th ined by th elements i elements i from the n from the n by adding by adding ted to the e ted to the e to the tran to the tran rgy require rgy require t cations in t cations in

uation uationE E photphot

s gives evid s gives evid ing distanc ing distanc to increasi to increasi ase across ase across ent give ev ent give ev of an atom of an atom ctron is rem ctron is rem p

p44 to a p to a p33 co co lled by their lled by their , which ca , which ca highest en highest en the p block the p block utral atom. utral atom. lectrons to lectrons to nergy state nergy state sition n = 1 sition n = 1 to remove to remove the gaseous the gaseous on on = =hhν ν (the (the

ence for the ence for the

of outer el of outer el g effective g effective period – d period – d idence for e idence for e ccur when a ccur when a oved from a oved from a nfiguration nfiguration be accoun be accoun rgy occupie rgy occupie have valen have valen The electro The electro a neutral at a neutral at of electron of electron o n = o n =∞∞(the(the one mole of one mole of state. It is t state. It is t equation is equation is existence o existence o ctrons from ctrons from uclear char uclear char e to the exi e to the exi lectron conf lectron conf n electron is n electron is different su different su s paired elec s paired elec ed for the s ed for the s d sub-level. d sub-level. e electrons e electrons n configurat n configurat m. The elec m. The elec in atoms a in atoms a convergenc convergenc electrons fr electrons fr e enthalpy e enthalpy iven in secti iven in secti main ener main ener the nucleus the nucleus e e tence of su tence of su igurations. igurations. removed fro removed fro -level. For e -level. For e trons are ea trons are ea ability of th ability of th Elements in Elements in in the p sub in the p sub ion of Na ion of Na++ f f tron tron d molecule d molecule e limit at e limit at om one mol om one mol change for t change for t on 1 of the I on 1 of the I y levels and y levels and -shells. -shells. m a differen m a differen ample, a ve ample, a ve ier to remo ier to remo e e rr s. s. e e he he B B tt yy e e

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Chapter 3: Periodicity – fast facts

3.1

3.1 The

The

Periodic

Table

The arrangement of elements in the Periodic Table helps

The arrangement of elements in the Periodic Table helps to predict their electron configuration.to predict their electron configuration.

•

• The Periodic Table arranges elements according to increasing atomic number / increasing number of protons.The Periodic Table arranges elements according to increasing atomic number / increasing number of protons.

•

• The horizontal rows are calledThe horizontal rows are called periodsperiods and vertical columns are called and vertical columns are called groupsgroups..

•

• The period number (The period number (nn) is the outer energy level that is occupied by electrons.) is the outer energy level that is occupied by electrons.

•

• Elements in the same period have outer Elements in the same period have outer electrons in the same energy electrons in the same energy level.level.

•

• The groups are numbered from 1 The groups are numbered from 1 to 18.to 18.

•

• Elements in the same group have the Elements in the same group have the same number of outer electrons and have same number of outer electrons and have similar chemical properties.similar chemical properties.

•

• The Periodic Table is arranged in 4 The Periodic Table is arranged in 4 blocks – s, p, d blocks – s, p, d and f – which and f – which are associated with the highest sub-levelare associated with the highest sub-level

occupied by electrons. occupied by electrons. •

• The position of an element is related to The position of an element is related to the electron configuration of its atoms. Magnesium, for example, is inthe electron configuration of its atoms. Magnesium, for example, is in

Period 3, as it has three occupied energy levels,

Period 3, as it has three occupied energy levels, and in Group 2, as and in Group 2, as there are two electrons in its outer energythere are two electrons in its outer energy level. It is in s block as it has outer electrons in the s sub-level.

level. It is in s block as it has outer electrons in the s sub-level. •

• Metals are found on the left of Metals are found on the left of the Periodic Table and non-metals on the right. Metalloids form a diagonalthe Periodic Table and non-metals on the right. Metalloids form a diagonal

staircase between the metals and non-metals. staircase between the metals and non-metals. •

• Group 1 = alkali Group 1 = alkali metals, Group 17 metals, Group 17 = halogens, = halogens, Group 18 = noble gases.Group 18 = noble gases.

•

• TheThe transition metalstransition metals are in the large section of are in the large section of d-blockd-block elements in the middle elements in the middle of the Periodic Table from Scof the Periodic Table from Sc

to Zn, etc. Zn is not

to Zn, etc. Zn is not a transition metal because it does not form ions with incomplete d a transition metal because it does not form ions with incomplete d sub-levels.sub-levels. •

• Lanthanoids and actinoids are metals in the first and second row of tLanthanoids and actinoids are metals in the first and second row of t he f block.he f block.

3.2

3.2 Periodic

Periodic

trends

Elements show trends in their

Elements show trends in their physical and chemical properties across periods and down groups.physical and chemical properties across periods and down groups.

•

• The chemical and physical properties of elements The chemical and physical properties of elements arranged in order of increasing atomic numbers varyarranged in order of increasing atomic numbers vary

periodically.

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•

• Patterns in ionic radii across a period are more complex.Patterns in ionic radii across a period are more complex.

•

• The ionic radii decrease from Groups 1 The ionic radii decrease from Groups 1 to 14 for the positive ions. The ions to 14 for the positive ions. The ions NaNa + +, Mg, Mg2 +2 +, Al, Al3 +3 + and Si and Si4 +4 + are are

isoelectronic

isoelectronic and have the same and have the same electron configuration (1selectron configuration (1s22 2s 2s22 2p 2p66 ). The decrease in ionic radius is due ). The decrease in ionic radius is due to the increase in nuclear charge with atomic number across the

to the increase in nuclear charge with atomic number across the period, which increases the attractionperiod, which increases the attraction between the nucleus and the outer

between the nucleus and the outer electrons.electrons. •

• The ionic radii decrease from Groups 14 to The ionic radii decrease from Groups 14 to 17 for the negative ions. The ions Si17 for the negative ions. The ions Si4–4–, P, P3–3–,, SS2–2– and Cl and Cl – – are are

isoelectronic and have the same electron arrangement (1s

isoelectronic and have the same electron arrangement (1s22 2s 2s22 2p 2p66 3s 3s22 3p 3p66). The decrease in ionic radius). The decrease in ionic radius is due to the increase in

is due to the increase in nuclear charge across the period.nuclear charge across the period. •

• The positive ions are smaller than the The positive ions are smaller than the negative ions in the same period, as the negative ions in the same period, as the former have one lessformer have one less

occupied electron shell. occupied electron shell. •

• TheThe firstfirst ionization energy (IE)ionization energy (IE) of an elementof an element is the minimum energy required to form one is the minimum energy required to form one mole of singlymole of singly

charged positive ions (M

charged positive ions (M++) by removing an electron from each atom (M) in the ) by removing an electron from each atom (M) in the gaseous state: M(g)gaseous state: M(g) →→ M M + +(g) +(g) + e

e – – (units: kJ mol (units: kJ mol –1 –1).). •

• First ionization energies decrease down a group. This is First ionization energies decrease down a group. This is due to the increased distance between due to the increased distance between the nucleusthe nucleus

and the outer energy level that reduc

and the outer energy level that reduc es the force of attraction between the nucleus and es the force of attraction between the nucleus and the outer electrons.the outer electrons. •

• Ionization energies increase along a period due to the increase in eIonization energies increase along a period due to the increase in e ffective nuclear charge, which causes theffective nuclear charge, which causes the

outer electrons to be held more tightly. outer electrons to be held more tightly. •

• There are regular discontinuities in the trend of There are regular discontinuities in the trend of increasing ionization energies along a period, due to theincreasing ionization energies along a period, due to the

existence of sub-levels within the main

existence of sub-levels within the main energy levels.energy levels. •

• Electron affinityElectron affinity is the energy change when is the energy change when one mole of electrons is added to one mole of gone mole of electrons is added to one mole of g aseous atoms toaseous atoms to

form one mole of gaseous ions: X(g) +

form one mole of gaseous ions: X(g) + ee – –→→_X_X – –(g)_(g)

•

• First electron affinities are usually endothermic, and increase along a period due First electron affinities are usually endothermic, and increase along a period due to increasing nuclear charge.to increasing nuclear charge.

•

• ElectronegativityElectronegativity is a measure of the is a measure of the attraction of a nucleus for bonding electrons.attraction of a nucleus for bonding electrons.

•

• Electronegativity increases along a period and decreases down a group.Electronegativity increases along a period and decreases down a group.

•

• The noble gases are not assigned The noble gases are not assigned electronegativities as they do not readily form bonds with other elements.electronegativities as they do not readily form bonds with other elements.

•

• The electronegativities of diagonal elements remain approximately the same as both the group and periodThe electronegativities of diagonal elements remain approximately the same as both the group and period

number increase. Boron and aluminium, for example, both have electronegativities of 1.6. number increase. Boron and aluminium, for example, both have electronegativities of 1.6. •

• The electronegativity of H is the same The electronegativity of H is the same as that of P.as that of P.

•

• Metals have low ionization energies and electronegativities; non-metals have high ionization energies andMetals have low ionization energies and electronegativities; non-metals have high ionization energies and

electronegativities. electronegativities.

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•

• The alkali metals react with water to produce hydrogen and the metal hydroxide. TThe alkali metals react with water to produce hydrogen and the metal hydroxide. T he resulting solution ishe resulting solution is

alkaline owing to the presence of hydroxide ions: 2M(s) +

alkaline owing to the presence of hydroxide ions: 2M(s) + 2H2H22O(l)O(l)→→ 2MOH(aq) + H 2MOH(aq) + H22(g)(g)

Group 17 Group 17

•

• The halogens are diatomic non-polar molecules.The halogens are diatomic non-polar molecules.

•

• They generally accept electrons and act asThey generally accept electrons and act as oxidizing agentsoxidizing agents: X: X₂₂ + 2e + 2e – –→→ 2X 2X – – •

• Reactivity decreases down the group, as the atom gets larger and Reactivity decreases down the group, as the atom gets larger and attraction for extra electrons decreases.attraction for extra electrons decreases.

The more reactive halogens, X

The more reactive halogens, X22,, displacedisplace the less reactive halogens, Y, from their compounds: the less reactive halogens, Y, from their compounds:

X

X22 + 2Y + 2Y – –→→ Y Y22+ 2X+ 2X – –

e.g. the more reactive Cl displaces Br: Cl

e.g. the more reactive Cl displaces Br: Cl22 + 2Br + 2Br – –→→ Br Br22 + 2Cl + 2Cl – –

•

• The halogens react with the Group 1 metals to The halogens react with the Group 1 metals to form ionicform ionic halideshalides: 2M + X: 2M + X₂₂→→ 2MX 2MX The most vigorous reaction occurs between the elements which are furthest

The most vigorous reaction occurs between the elements which are furthest apart in the Periodic Table.apart in the Periodic Table.

Period 3 oxides Period 3 oxides

•

• Oxides change from basic through amphoteric to acidic across a period.Oxides change from basic through amphoteric to acidic across a period.

Formula and Formula and state at room state at room temperature temperature Na

Na22O(s) O(s) MgO(s) MgO(s) AlAl22OO33(s) (s) SiOSiO22(s) (s) PP44OO1010(s)/(s)/

P P44OO66(s)(s) SO SO33(l)/(l)/ SO SO22(g)(g) Cl Cl22OO77(l)/(l)/ Cl Cl22O(g)O(g) Structure

Structure Ionic Ionic Giant covalent Giant covalent Molecular Molecular covalentcovalent Acid/base

Acid/base character character

Ba

Basisic c AmAmphphototerericic AcAcididicic

Na

Na22O(s) + HO(s) + H22O(l)O(l)→→ 2NaOH(aq) 2NaOH(aq)

MgO(s) + H

MgO(s) + H22O(l)O(l)→→ Mg(OH) Mg(OH)22(aq)(aq)

P

P44OO1010(s) + 6H(s) + 6H22O(l)O(l)→→ 4H 4H33POPO44(aq)(aq)

SO

SO33(g) + H(g) + H22O(l)O(l)→→ H H22SOSO44(aq)(aq)

As SiO

As SiO22(s) is insoluble it does not change the pH if(s) is insoluble it does not change the pH if

added to H added to H22O.O.

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13.1

13.1 First-row

First-row

d-block

elements

The transition elements have characteristic properties; these properties are related to their all The transition elements have characteristic properties; these properties are related to their all

having incomplete d sub-levels. having incomplete d sub-levels.

•

• Transition metals have partially filled d orbitals in their atoms or ions.Transition metals have partially filled d orbitals in their atoms or ions.

•

• Zn is not a transition element because it has Zn is not a transition element because it has a full d sub-level in a full d sub-level in its atoms and ions.its atoms and ions.

•

• Characteristic properties include: variable oxidation number, complex ion Characteristic properties include: variable oxidation number, complex ion formation with ligands, existence offormation with ligands, existence of

coloured compounds, have catalytic and

coloured compounds, have catalytic and magnetic properties.magnetic properties. •

• Multiple oxidation states arise because the 3d and 4s sub-Multiple oxidation states arise because the 3d and 4s sub- levels are close in energy and levels are close in energy and both are involved inboth are involved in

bonding. bonding. •

• All d-block elements except Sc show an oxidation state of +2.All d-block elements except Sc show an oxidation state of +2.

•

• All d-block elements except Zn show an All d-block elements except Zn show an oxidation state of +3.oxidation state of +3.

•

• A ligand is a molecule or negative ion that donates a A ligand is a molecule or negative ion that donates a pair of electrons to a central metal ion to form a covalentpair of electrons to a central metal ion to form a covalent

(coordinate) bond. They are Lewis bases. (coordinate) bond. They are Lewis bases. •

• ComplexComplex ions ions are formed when a central metal ion is are formed when a central metal ion is bonded to a ligand with a coordinate bond. Ebonded to a ligand with a coordinate bond. E xamplesxamples

include [Fe(H

include [Fe(H22O)O)66]]3+3+,, [Fe(CN) [Fe(CN)66]]3–3–, [CuCl, [CuCl44]]2–2–, and [Ag(NH, and [Ag(NH33))22]]++..

•

• The charge on a complex ion is The charge on a complex ion is the sum of the charges of the sum of the charges of the metal ion and the ligands.the metal ion and the ligands.

•

• Transition metals act as heterogeneous catalysts as they can provide a surface Transition metals act as heterogeneous catalysts as they can provide a surface for reaction: they use the 3dfor reaction: they use the 3d

and 4s electrons to form weak bonds to reactant molecules. and 4s electrons to form weak bonds to reactant molecules. •

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Chapter 4: Chemical bonding and structure fast

facts

4.1

4.1 Ionic

Ionic

bonding

and

structure

Ionic compounds consist of ions held together in

Ionic compounds consist of ions held together in lattice structures by ionic bonds.lattice structures by ionic bonds.

•

• An ion is a charged particle.An ion is a charged particle.

•

• The number of charges on an The number of charges on an ion is equal to the number of ion is equal to the number of electrons lost (positive ion) or gained (negativeelectrons lost (positive ion) or gained (negative

ion) by an atom. ion) by an atom. •

• Metals lose electrons to form positive ions (cations); non-metals gain electrons to form negative ions (anions).Metals lose electrons to form positive ions (cations); non-metals gain electrons to form negative ions (anions).

•

• The charge on an ion can The charge on an ion can usually be predicted from the group usually be predicted from the group of the element in the Periodic Table; transitionof the element in the Periodic Table; transition

metal elements can form more than one ion. metal elements can form more than one ion. •

• Common polyatomic ions include: OHCommon polyatomic ions include: OH – –, HCO, HCO₃₃ – –, NO, NO₃₃ – –, CO, CO₃₃2–2–, SO, SO₄₄2–2–, PO, PO₄₄3–3–, NH, NH₄₄++..

•

• Ionic compounds consist of ions held together by Ionic compounds consist of ions held together by forces of electrostatic attraction.forces of electrostatic attraction.

•

• Ionic compounds are electrically neutral, as they consist of a lattice in Ionic compounds are electrically neutral, as they consist of a lattice in which the total number of positivewhich the total number of positive

charges is balanced by the

charges is balanced by the total number of negative charges. The formula of the compound is expressed total number of negative charges. The formula of the compound is expressed as itsas its simplest ratio, e.g. the ions X

simplest ratio, e.g. the ions Xmm₊₊

and Y and Ynn_–_–

will form the compound X will form the compound XnnYYmm..

•

• In the ionic lattice, each ion is surrounded by In the ionic lattice, each ion is surrounded by a fixed number of ions of a fixed number of ions of the opposite charge, known as thethe opposite charge, known as the

coordination number. coordination number.

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4.3

4.3 Covalent

Covalent

structures

Lewis (electron dot) structures show the electron domains in the valence

Lewis (electron dot) structures show the electron domains in the valence shell and are used toshell and are used to predict molecular shape.

predict molecular shape.

•

• Lewis (electron dot) structures show all the valence electrons of the atoms in Lewis (electron dot) structures show all the valence electrons of the atoms in the molecule or polyatomic ion.the molecule or polyatomic ion.

•

• The octet rule refers to the fact that most atoms form a The octet rule refers to the fact that most atoms form a stable arrangement with eight electrons in their outerstable arrangement with eight electrons in their outer

shell. shell. •

• Exceptions to the octet rule include:Exceptions to the octet rule include:

less than an octet – BeCl

less than an octet – BeCl22, BF, BF33 (central atom very small) (central atom very small)

expanded octet – PCl

expanded octet – PCl₅₅, SF, SF₆₆ (central atom from third period or beyond). (central atom from third period or beyond). •

• VSEPR theory: the total number of electron domains determines their geometrical arrangement by maximumVSEPR theory: the total number of electron domains determines their geometrical arrangement by maximum

repulsion; the shape of the

repulsion; the shape of the molecule then depends on the number molecule then depends on the number of bonding pairs within this of bonding pairs within this arrangement.arrangement. Number

Number of of charge charge centres centres Number Number of of bonding bonding pairs pairs Shape Shape of of moleculemolecule

2

2 2 2 linearlinear 3

3 3 3 planar planar triangulartriangular 3

3 2 2 V-shapedV-shaped 4

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•

• The polarity of a molecule depends on:The polarity of a molecule depends on:

i

i the the polarities polarities of of its its bondsbonds ii

ii its moleculaits molecular shape – r shape – whether cancellatiowhether cancellation occurs n occurs between the between the polar bonds.polar bonds. •

• Coordinate bonds form when both the shared electrons originate from the sCoordinate bonds form when both the shared electrons originate from the s ame atom.ame atom.

4.4

4.4 Intermolecula

Intermolecula

r

forces

The physical properties of molecular substances result from different types

The physical properties of molecular substances result from different types of forces between their molecules.of forces between their molecules. •

• The forces between molecules are largely determined by The forces between molecules are largely determined by the charge separation within the molecule:the charge separation within the molecule:

•

• non-polar moleculesnon-polar molecules London (dispersion) forces London (dispersion) forces

•

• polar moleculespolar molecules dipole–dipole attraction dipole–dipole attraction

•

• polar molecules in which H polar molecules in which H is bonded to O, N, or Fis bonded to O, N, or F  hydrogen bonding. hydrogen bonding.

•

• van der Waals forces refer to London (dispersion) and van der Waals forces refer to London (dispersion) and dipole–dipole attractions.dipole–dipole attractions.

•

• In order of strength:In order of strength:

London (dispersion) < dipole–dipole < hydrogen bonding London (dispersion) < dipole–dipole < hydrogen bonding •

• The stronger the intermolecular force, the lower the volatility (higher boiling point).The stronger the intermolecular force, the lower the volatility (higher boiling point).

•

• Polar substances are more soluble in water and less Polar substances are more soluble in water and less soluble in non-polar solvents.soluble in non-polar solvents.

•

• Covalent compounds are generally not good electrical conductors, unless they are able to ionize in Covalent compounds are generally not good electrical conductors, unless they are able to ionize in solution,solution,

e.g. HCl(aq). e.g. HCl(aq).