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PERIODICITYPERIODICITYPERIODICITYPERIODICITY
Periodic TablePeriodic Table• Dmitri Mendeleev developed the Dmitri Mendeleev developed the
modern periodic table. Argued modern periodic table. Argued that element properties are that element properties are periodic functions of their periodic functions of their atomic weights.atomic weights.
• We now know that element We now know that element properties are periodic functions properties are periodic functions of their of their ATOMIC NUMBERSATOMIC NUMBERS..
PeriodsPeriods in the Periodic Table in the Periodic Table
GroupsGroups in the Periodic Table in the Periodic Table
Regions of the Periodic Regions of the Periodic TableTable
Metals, Nonmetals, and Metalloids
– Three classes of elements are metals, nonmetals, and metalloids.
– Across a period, the properties of elements become less metallic and more nonmetallic.
6.1
Metals, Nonmetals, and Metalloids
»Metals, Metalloids, and Nonmetals in the Periodic Table
6.1
Metals, Nonmetals, and Metalloids
»Metals, Metalloids, and Nonmetals in the Periodic Table
6.1
Metals, Nonmetals, and Metalloids
»Metals, Metalloids, and Nonmetals in the Periodic Table
6.1
Metals, Nonmetals, and Metalloids
»Metals, Metalloids, and Nonmetals in the Periodic Table
6.1
Metals, Nonmetals, and Metalloids
– Metals• Metals are good conductors of heat and electric
current.– 80% of elements are metals.
– Metals have a high luster, are ductile, and are malleable.
6.1
Metals, Nonmetals, and Metalloids
» Uses of Iron, Copper, and Aluminum
6.1
Metals, Nonmetals, and Metalloids
» Uses of Iron, Copper, and Aluminum
6.1
Metals, Nonmetals, and Metalloids
» Uses of Iron, Copper, and Aluminum
6.1
Metals, Nonmetals, and Metalloids
– Nonmetals• In general, nonmetals are poor conductors of heat
and electric current.– Most nonmetals are gases at room temperature.– A few nonmetals are solids, such as sulfur and
phosphorus.– One nonmetal, bromine, is a dark-red liquid.
6.1
Metals, Nonmetals, and Metalloids
– Metalloids• A metalloid generally has properties that are similar
to those of metals and nonmetals.
• The behavior of a metalloid can be controlled by changing conditions.
6.1
http://www.webelements.com/webelements/elements/text/Si/geol.html
Element Element AbundanceAbundance
FeC AlO Si
HydrogenHydrogenHydrogenHydrogen
Shuttle main engines use Shuttle main engines use HH22 and O and O22 The Hindenburg crash, The Hindenburg crash,
May 1939.May 1939.
Group 1A: Alkali Group 1A: Alkali MetalsMetals
Group 1A: Alkali Group 1A: Alkali MetalsMetals
Cutting sodium metalCutting sodium metal
Reaction of potassium + H2O
MagnesiumMagnesium
Magnesium Magnesium oxideoxide
Group 2A: Alkaline Earth MetalsGroup 2A: Alkaline Earth Metals
Calcium Carbonate—Calcium Carbonate—LimestoneLimestone
The Appian Way, ItalyThe Appian Way, Italy Champagne cave carved into Champagne cave carved into chalk in Francechalk in France
Group 3A: B, Al, Ga, In, Group 3A: B, Al, Ga, In, TlTl
Group 3A: B, Al, Ga, In, Group 3A: B, Al, Ga, In, TlTl
AluminumAluminum
Boron halidesBoron halides BF BF33 & BI & BI33
Gems & MineralsGems & Minerals
• Sapphire:Sapphire: Al Al22OO33
with Fewith Fe3+3+ or Ti or Ti3+3+ impurity gives impurity gives blue whereas Vblue whereas V3+3+ gives violet.gives violet.
• Ruby:Ruby: Al Al22OO33
with Crwith Cr3+3+ impurityimpurity
Group 4A: C, Si, Ge, Sn, Group 4A: C, Si, Ge, Sn, PbPb
Group 4A: C, Si, Ge, Sn, Group 4A: C, Si, Ge, Sn, PbPb
Quartz, SiOQuartz, SiO22
DiamondDiamond
Group 5A: N, P, As, Sb, BiGroup 5A: N, P, As, Sb, BiGroup 5A: N, P, As, Sb, BiGroup 5A: N, P, As, Sb, Bi
White and red White and red phosphorusphosphorus
Ammonia, NHAmmonia, NH33
PhosphoruPhosphoruss
• Phosphorus first isolated by Brandt from urine, 1669
Group 6A: O, S, Se, Te, PoGroup 6A: O, S, Se, Te, PoGroup 6A: O, S, Se, Te, PoGroup 6A: O, S, Se, Te, Po
Sulfuric acid dripping from Sulfuric acid dripping from snot-tite in cave in Mexicosnot-tite in cave in Mexico
Sulfur from Sulfur from a volcanoa volcano
Group 7A: Group 7A: F, Cl, Br, I, AtF, Cl, Br, I, AtGroup 7A: Group 7A:
F, Cl, Br, I, AtF, Cl, Br, I, At
Group 8A: Group 8A: He, Ne, Ar, Kr, Xe, RnHe, Ne, Ar, Kr, Xe, Rn
Group 8A: Group 8A: He, Ne, Ar, Kr, Xe, RnHe, Ne, Ar, Kr, Xe, Rn
• Lighter than air balloons
• “Neon” signs
XeOFXeOF44XeOFXeOF44
Transition ElementsTransition ElementsTransition ElementsTransition Elements
Lanthanides and actinidesLanthanides and actinides
Iron in air gives Iron in air gives iron(III) oxideiron(III) oxide
LithiumLithiumLithiumLithium
Group 1AGroup 1AAtomic number = 3Atomic number = 31s1s222s2s11 ---> 3 total electrons ---> 3 total electrons
1s
2s
3s3p
2p
BerylliumBerylliumBerylliumBeryllium
Group 2AGroup 2A
Atomic number = 4Atomic number = 4
1s1s222s2s22 ---> 4 total ---> 4 total electronselectrons
1s
2s
3s3p
2p
BoronBoronBoronBoron
Group 3AGroup 3AAtomic number = 5Atomic number = 51s1s2 2 2s2s2 2 2p2p11 ---> ---> 5 total electrons5 total electrons
1s
2s
3s3p
2p
CarbonCarbonCarbonCarbonGroup 4AGroup 4AAtomic number = 6Atomic number = 61s1s2 2 2s2s2 2 2p2p22 ---> ---> 6 total electrons6 total electrons
1s
2s
3s3p
2p
NitrogenNitrogenNitrogenNitrogen
Group 5AGroup 5AAtomic number = 7Atomic number = 71s1s2 2 2s2s2 2 2p2p33 ---> ---> 7 total electrons7 total electrons
1s
2s
3s3p
2p
OxygenOxygenOxygenOxygen
Group 6AGroup 6AAtomic number = 8Atomic number = 81s1s2 2 2s2s2 2 2p2p44 ---> ---> 8 total electrons8 total electrons
1s
2s
3s3p
2p
FluorineFluorineFluorineFluorine
Group 7AGroup 7AAtomic number = 9Atomic number = 91s1s2 2 2s2s2 2 2p2p55 ---> ---> 9 total electrons9 total electrons
1s
2s
3s3p
2p
NeonNeonNeonNeon
Group 8AGroup 8AAtomic number = 10Atomic number = 101s1s2 2 2s2s2 2 2p2p66 ---> ---> 10 total electrons10 total electrons
1s
2s
3s3p
2p
Colors of Transition Colors of Transition Metal CompoundsMetal Compounds
Iron Cobalt Nickel Copper Zinc
PERIODIC
PERIODIC TRENDS
TRENDS
PERIODIC
PERIODIC TRENDS
TRENDS
General Periodic TrendsGeneral Periodic Trends• Atomic and ionic sizeAtomic and ionic size• Ionization energyIonization energy• Electron affinityElectron affinity• ElectronegativityElectronegativity
Higher effective nuclear chargeElectrons held more tightly
Larger orbitals.Electrons held lesstightly.
Effective Nuclear Charge, Z*Effective Nuclear Charge, Z*Effective Nuclear Charge, Z*Effective Nuclear Charge, Z*• Explains why E(2s) < E(2p)Explains why E(2s) < E(2p)
• Z* is the nuclear charge experienced by the outermost electrons.Z* is the nuclear charge experienced by the outermost electrons. Is the result of the nuclear attraction being blocked by the core Is the result of the nuclear attraction being blocked by the core electrons. Nuclear attraction increases with an increase in protonselectrons. Nuclear attraction increases with an increase in protons
• Estimate Z* by --> [ Estimate Z* by --> [ Z - (no. core electrons) Z - (no. core electrons) ]]
• Charge felt by 2s e- in Li Z* = 3 - 2 = 1Charge felt by 2s e- in Li Z* = 3 - 2 = 1
• Be Be Z* = 4 - 2 = 2Z* = 4 - 2 = 2
• B B Z* = 5 - 2 = 3Z* = 5 - 2 = 3 and so on! and so on!
Effective Nuclear Charge, Z*Effective Nuclear Charge, Z*Effective Nuclear Charge, Z*Effective Nuclear Charge, Z*• Shielding effect remains constant across a period. Shielding effect remains constant across a period.
As the nuclear attraction increases across the As the nuclear attraction increases across the shielding effect is less effective.shielding effect is less effective.
• Shielding effect increases down a group thus Shielding effect increases down a group thus effectively blocking any increase in nuclear effectively blocking any increase in nuclear attraction.attraction.
• Electrons with a higher quantum number have more Electrons with a higher quantum number have more kinetic energy and thus are less affected by the kinetic energy and thus are less affected by the nuclear charge.nuclear charge.
Each of these forces need to be accounted for in Each of these forces need to be accounted for in each trend.each trend.
EffectiveEffective Nuclear Charge, Nuclear Charge, Z*Z*
• Atom Z* Experienced by Electrons in Valence Orbitals
• Li +1.28• Be -------• B +2.58• C +3.22• N +3.85• O +4.49• F +5.13
Increase in Increase in Z* across a Z* across a periodperiod
Periodic Trend in Periodic Trend in the Reactivity of the Reactivity of
Alkali Metals Alkali Metals with Waterwith Water
Periodic Trend in Periodic Trend in the Reactivity of the Reactivity of
Alkali Metals Alkali Metals with Waterwith WaterLithiumLithium
SodiumSodium PotassiumPotassium
Atomic Atomic SizeSize
Atomic Atomic SizeSize
• Size goes UPSize goes UP on going down a on going down a group. group.
• Because electrons are added Because electrons are added further from the nucleus, there is further from the nucleus, there is less attraction, due to an increase less attraction, due to an increase in sheilding effectiveness and in in sheilding effectiveness and in increase in kinetic energy.increase in kinetic energy.
• Size goes UPSize goes UP on going down a on going down a group. group.
• Because electrons are added Because electrons are added further from the nucleus, there is further from the nucleus, there is less attraction, due to an increase less attraction, due to an increase in sheilding effectiveness and in in sheilding effectiveness and in increase in kinetic energy.increase in kinetic energy.
Atomic SizeAtomic SizeAtomic SizeAtomic Size
• Size goes UPSize goes UP on going down a on going down a group. group.
• Because electrons are added Because electrons are added further from the nucleus, there is further from the nucleus, there is less attraction, due to an increase less attraction, due to an increase in sheilding effectiveness and in in sheilding effectiveness and in increase in kinetic energy.increase in kinetic energy.
• Size goes UPSize goes UP on going down a on going down a group. group.
• Because electrons are added Because electrons are added further from the nucleus, there is further from the nucleus, there is less attraction, due to an increase less attraction, due to an increase in sheilding effectiveness and in in sheilding effectiveness and in increase in kinetic energy.increase in kinetic energy.
General Outline for Trends
• Trend-define• Down a group• Nuclear attraction-define
once– Trend, effect
– Shielding effect-define once• Trend, effect
– Kinetic energy-define once• Trend, effect
• Across a period• Nuclear attraction
– Trend, effect
– Shielding effect• Trend, effect
– Kinetic energy• Trend, effect
Atomic Radius• Atomic radius is the distance from the nucleus to
the valance electrons. – Nuclear attraction (the attraction of the protons in the
nucleus on valance electrons) increases going down a group. This should pull the electrons in closer to the nucleus.
– Shielding effect (the blocking of nuclear attractions by core electrons) Shielding effect increases down a group offsetting the increase in nuclear attraction.
– Kinetic energy (the energy of valance electrons associated with principle energy levels) increases down a group allowing the valance electrons to orbit farther from the nucleus increasing atomic radius.
Atomic Radius
– Nuclear attraction increases across a period. This should pull the electrons in closer to the nucleus decreasing atomic radius.
– Shielding effect remains constant across a period not offsetting nuclear attraction.
– Kinetic energy remains constant across a period so effective nuclear attraction is greater and the atomic radius decreases.
Atomic RadiiAtomic RadiiAtomic RadiiAtomic Radii
Figure 8.9Figure 8.9
Atomic SizeAtomic SizeAtomic SizeAtomic SizeSize Size decreasesdecreases across a period owing across a period owing
to increase in Z*. Each added electron to increase in Z*. Each added electron feels a greater and greater + charge.feels a greater and greater + charge.
LargeLarge SmallSmall
Ion SizesIon SizesIon SizesIon Sizes
Li,152 pm3e and 3p
Li+, 60 pm2e and 3 p
+Does the size goDoes the size goup or down up or down when losing an when losing an electron to form electron to form a cation?a cation?
Does the size goDoes the size goup or down up or down when losing an when losing an electron to form electron to form a cation?a cation?
Ion SizesIon SizesIon SizesIon Sizes
• CATIONSCATIONS are are SMALLERSMALLER than the than the atoms from which they come.atoms from which they come.
• The electron/proton attraction has gone The electron/proton attraction has gone UP and so size UP and so size DECREASESDECREASES..
Li,152 pm3e and 3p
Li +, 78 pm2e and 3 p
+Forming Forming a cation.a cation.Forming Forming a cation.a cation.
Ion SizesIon SizesIon SizesIon Sizes
F,64 pm9e and 9p
F- , 136 pm10 e and 9 p
-Does the size go up or Does the size go up or down when gaining an down when gaining an electron to form an electron to form an anion?anion?
Does the size go up or Does the size go up or down when gaining an down when gaining an electron to form an electron to form an anion?anion?
Ion SizesIon SizesIon SizesIon Sizes
• ANIONSANIONS are are LARGERLARGER than the atoms from which than the atoms from which they come.they come.
• The electron/proton attraction has gone DOWN and The electron/proton attraction has gone DOWN and so size so size INCREASESINCREASES..
• Trends in ion sizes are the same as atom sizes. Trends in ion sizes are the same as atom sizes.
Forming Forming an anion.an anion.Forming Forming an anion.an anion.F, 71 pm
9e and 9pF-, 133 pm10 e and 9 p
-
Trends in Ion SizesTrends in Ion SizesTrends in Ion SizesTrends in Ion Sizes
Figure 8.13Figure 8.13
Ionic Size• Ionic size is the distance from the nucleus to the
valence electrons after an atom has lost or gained electrons.
• Cations form when an atom loses one or more electrons.
• Cations are smaller than the atoms from which they form
• Ionic size - Cations– Effective nuclear charge increases dramatically when
electrons are removed.– Shielding effect decreases compared to the atom
because valence electrons are lost and some or all of the core electrons become valence electrons.
– Kinetic energy the new valence electrons have less kinetic energy to resist the pull of the nucleus.
Ionic Size• Anions form when an atom gains one or more
electrons• Ionic size - Anions
– After the addition of valence electron(s) the nuclear attraction is diluted.
– Shielding effect remains still resisting the nuclear attraction.
– Kinetic energy increases because of additional repulsion due to more electrons in the valence shell increasing the anions size.
– Anions are larger than the atoms from which they form
Ionization EnergyIonization EnergyIonization EnergyIonization Energy
IE = energy required to remove an electron IE = energy required to remove an electron from an atom in the gas phase.from an atom in the gas phase.
Mg (g) + 738 kJ ---> MgMg (g) + 738 kJ ---> Mg++ (g) + e- (g) + e-
Mg (g) + 738 kJ ---> MgMg (g) + 738 kJ ---> Mg++ (g) + e- (g) + e-
MgMg+ + (g) + 1451 kJ ---> Mg(g) + 1451 kJ ---> Mg2+2+ (g) + e- (g) + e-
MgMg++ has 12 protons and only 11 electrons. has 12 protons and only 11 electrons. Therefore, IE for MgTherefore, IE for Mg++ > Mg. > Mg.
IE = energy required to remove an IE = energy required to remove an electron from an atom in the gas phase.electron from an atom in the gas phase.
Ionization EnergyIonization EnergyIonization EnergyIonization Energy
Mg (g) + 735 kJ ---> MgMg (g) + 735 kJ ---> Mg++ (g) + e- (g) + e-
MgMg+ + (g) + 1451 kJ ---> Mg(g) + 1451 kJ ---> Mg2+2+ (g) + e- (g) + e-
MgMg2+2+ (g) + 7733 kJ ---> Mg (g) + 7733 kJ ---> Mg3+3+ (g) + e- (g) + e-
Energy cost is very high to dip into a Energy cost is very high to dip into a shell of lower n. shell of lower n.
Ionization EnergyIonization EnergyIonization EnergyIonization Energy
General Periodic General Periodic TrendsTrends• Atomic and ionic sizeAtomic and ionic size
• Ionization energyIonization energy• Electron affinityElectron affinity
Higher Z*.Electrons heldmore tightly.
Larger orbitals.Electrons held lesstightly.
Trends in Ionization EnergyTrends in Ionization EnergyTrends in Ionization EnergyTrends in Ionization Energy
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 350
500
1000
1500
2000
2500
1st Ionization energy (kJ/mol)
Atomic NumberH Li Na K
HeNe
ArKr
Trends in Ionization EnergyTrends in Ionization EnergyTrends in Ionization EnergyTrends in Ionization Energy• IE increases across a period IE increases across a period
because Z* increases.because Z* increases.• Metals lose electrons more Metals lose electrons more
easily than nonmetals.easily than nonmetals.• Metals are good reducing Metals are good reducing
agents.agents.• Nonmetals lose electrons with Nonmetals lose electrons with
difficulty.difficulty.
Trends in Ionization Trends in Ionization EnergyEnergy
Trends in Ionization Trends in Ionization EnergyEnergy
• IE decreases down a group IE decreases down a group
• Because size increases.Because size increases.
• Reducing ability generally Reducing ability generally increases down the periodic increases down the periodic table. table.
• See reactions of Li, Na, KSee reactions of Li, Na, K
Mg (g) + 735 kJ ---> MgMg (g) + 735 kJ ---> Mg++ (g) + e- (g) + e-
MgMg+ + (g) + 1451 kJ ---> Mg(g) + 1451 kJ ---> Mg2+2+ (g) + e- (g) + e-
MgMg2+2+ (g) + 7733 kJ ---> Mg (g) + 7733 kJ ---> Mg3+3+ (g) + e- (g) + e-
Energy cost is very high to dip into a Energy cost is very high to dip into a shell of lower n. shell of lower n. This is why ox. no. = Group no.This is why ox. no. = Group no.
Ionization EnergyIonization EnergySee Screen 8.12See Screen 8.12
Ionization EnergyIonization EnergySee Screen 8.12See Screen 8.12
Ionization Energy• Ionization energy is the energy
needed to remove an electron from an atom.
• Nuclear attraction
– Increases down a group holding the electrons tighter.
– Shielding effect increases down a group offsetting the increase in nuclear attraction.
– Kinetic energy increases down a group giving the electrons greater initial energy. This reduces the additional energy needed to remove an electron.
• Nuclear attraction increases across a period holding the electrons tighter.
• Shielding effect is constant across and does not offset the increase in nuclear attraction.
• Kinetic energy remains constant across. With the same initial energy valence electrons are increasingly harder to remove due to the greater effective nuclear charge.
Electron AffinityElectron Affinity
A few elements A few elements GAINGAIN electrons to electrons to form form anionsanions..
Electron affinity is the energy Electron affinity is the energy involved when an atom gains an involved when an atom gains an electron to form an anion.electron to form an anion.
A(g) + e- ---> AA(g) + e- ---> A--(g) E.A. = (g) E.A. = ∆E∆E
Electron Affinity of OxygenElectron Affinity of Oxygen
∆∆E is E is EXOEXOthermic thermic because O has because O has an affinity for an an affinity for an e-.e-.
[He] O atom
EA = - 141 kJ
+ electron
O [He] - ion
Electron Affinity of Electron Affinity of NitrogenNitrogen
∆∆E is E is zero zero for Nfor N- -
due to electron-due to electron-electron electron repulsions.repulsions.
EA = 0 kJ
[He] N atom
[He] N- ion
+ electron
• See Figure 8.12 and See Figure 8.12 and Appendix FAppendix F
• Affinity for electron Affinity for electron increases across a period increases across a period (EA becomes more (EA becomes more positive).positive).
• Affinity decreases down Affinity decreases down a group (EA becomes a group (EA becomes less positive).less positive).
Atom EAAtom EAFF +328 kJ+328 kJClCl +349 kJ+349 kJBrBr +325 kJ+325 kJII +295 kJ+295 kJ
Atom EAAtom EAFF +328 kJ+328 kJClCl +349 kJ+349 kJBrBr +325 kJ+325 kJII +295 kJ+295 kJ
Trends in Electron AffinityTrends in Electron Affinity
Trends in Electron AffinityTrends in Electron Affinity
Electronegativity Values
See page 177 in text
Electronegativity• Electronegativity is the tendency
of an atom to remove an electron from another atom when forming a compound.
• Nuclear attraction
– Increases down a group attracting the electrons more.
– Shielding effect increases down a group offsetting the increase in nuclear attraction.
– Kinetic energy increases down a group giving the atom a larger radius and increasing the proximity of the nucleus to adjacent electrons decreasing electronegativity
• Nuclear attraction increases across a period attracting electrons more.
• Shielding effect and kinetic energy are constant across. This increases effective nuclear charge allowing the atom to remove electron from other atoms with lesser electronegativity.