periodic trends trends in properties on the periodic table
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Periodic TrendsPeriodic Trends
Trends in Properties on the Trends in Properties on the Periodic TablePeriodic Table
The PlanThe Plan
Essential Question: What causes the trends Essential Question: What causes the trends of the properties in the periodic table?of the properties in the periodic table?
Discuss Some Properties of AtomsDiscuss Some Properties of Atoms
Explore the TrendsExplore the Trends
Try to Explain the TrendsTry to Explain the Trends
Effective Nuclear ChargeEffective Nuclear Charge
Effective Nuclear Charge Effective Nuclear Charge - (Z- (Zeffeff) – the ) – the charge an electron “feels” from the charge an electron “feels” from the nucleusnucleus
ZZeffeff = Z – S, where Z is the atomic number = Z – S, where Z is the atomic number and S is the shielding experienced by the and S is the shielding experienced by the outer electronsouter electrons
The electrons in the outer energy levels The electrons in the outer energy levels don’t feel the full charge of the nucleus don’t feel the full charge of the nucleus because the core electrons help shield because the core electrons help shield them from the nucleus.them from the nucleus.
Atomic RadiusAtomic Radius
Atomic radiusAtomic radius – the – the radius of an atomradius of an atom
Several methods of Several methods of determining the determining the radius - usually radius - usually measure the distance measure the distance between two atomsbetween two atoms
Not all values are Not all values are completely consistent completely consistent with each other.with each other.
Ionization EnergyIonization Energy
Ionization EnergyIonization Energy – the energy required to – the energy required to remove one electron from an atomremove one electron from an atom
Essentially this is the process of making a Essentially this is the process of making a positive ion.positive ion.
X X X X++ + e + e--
ElectronegativityElectronegativity
ElectronegativityElectronegativity – the ability of an atom in – the ability of an atom in a compound to attract electrons to itselfa compound to attract electrons to itself
Electrons in compounds spend the most Electrons in compounds spend the most time around atoms with high time around atoms with high electronegativities.electronegativities.
Elements with high electronegativities Elements with high electronegativities have partial negative charges in have partial negative charges in compounds.compounds.
Periodic Trends LabPeriodic Trends Lab
In your lab groups, predict what trends you In your lab groups, predict what trends you think might occur down a family and think might occur down a family and across a period for each of the properties across a period for each of the properties we discussed:we discussed:
Effective nuclear chargeEffective nuclear chargeAtomic radiusAtomic radiusIonization energyIonization energyElectronegativityElectronegativity
Record on the index card for discussion laterRecord on the index card for discussion later
Effective Nuclear ChargeEffective Nuclear Charge
As you travel left to right across a period:As you travel left to right across a period:Atomic number increasesAtomic number increasesShielding stays roughly the sameShielding stays roughly the sameTherefore ZTherefore Zeffeff increases significantly across a increases significantly across a
periodperiodAs you travel down a familyAs you travel down a family
Atomic number increases sharplyAtomic number increases sharplyShielding increases sharplyShielding increases sharplyZZeffeff does increase down a family but not as does increase down a family but not as
much as you might expect.much as you might expect.
Atomic RadiusAtomic RadiusAs you travel left to right across a period:As you travel left to right across a period:
Effective nuclear charge increasesEffective nuclear charge increasesElectrons are being added to the same n shellElectrons are being added to the same n shelln values have somewhat to do with distance n values have somewhat to do with distance
from the nucleus.from the nucleus.Size of atoms shrink as you move to the right.Size of atoms shrink as you move to the right.
As you travel down a familyAs you travel down a familyEffective nuclear charge increases more Effective nuclear charge increases more
slowlyslowlyElectrons are added to n shells farther awayElectrons are added to n shells farther awaySize of atoms increase down the familySize of atoms increase down the family
Ionization EnergyIonization Energy
As you travel left to right across a periodAs you travel left to right across a periodEffective nuclear charge increasesEffective nuclear charge increasesHarder to remove an electron therefore…Harder to remove an electron therefore… Ionization Energy increasesIonization Energy increases
As you travel down a familyAs you travel down a familyEffective nuclear charge increases slowlyEffective nuclear charge increases slowlyOuter electrons are farther away from the Outer electrons are farther away from the
nucleusnucleus Ionization Energy decreasesIonization Energy decreases
Ionization EnergyIonization Energy
Ionization EnergyIonization Energy
ElectronegativityElectronegativity
As you travel left to right across a period:As you travel left to right across a period:Effective nuclear charge increases stronglyEffective nuclear charge increases stronglyElectronegativity increasesElectronegativity increases
As you travel down a familyAs you travel down a familyEffective nuclear charge increases slowlyEffective nuclear charge increases slowlyOuter electrons are being added in shells Outer electrons are being added in shells
farther and farther awayfarther and farther awayElectronegativity decreasesElectronegativity decreases
ElectronegativityElectronegativity
Ionic RadiusIonic Radius
Ionic RadiusIonic Radius – size of an ion – size of an ion
Consider two different relationshipsConsider two different relationshipsRelationship between atom and ionRelationship between atom and ionRelationship between ions and atoms with the Relationship between ions and atoms with the
same number of electronssame number of electrons““isoelectronic series”isoelectronic series”
Ionic RadiusIonic Radius
Ionic vs. AtomicIonic vs. Atomic
Number of protons always stays the sameNumber of protons always stays the sameFor negative ions (anions)For negative ions (anions)
Electrons are added to the same outer shellElectrons are added to the same outer shellElectron-electron repulsions increaseElectron-electron repulsions increaseAnions are larger than their atomsAnions are larger than their atoms
For positive ions (cations)For positive ions (cations)Electrons are removed to leave one less shellElectrons are removed to leave one less shelln shells describe distance from nucleusn shells describe distance from nucleusCations are smaller than their atomsCations are smaller than their atoms
Ionic RadiusIonic Radius
Isoelectronic seriesIsoelectronic series
All have the same number of electronsAll have the same number of electronsNumber of protons changesNumber of protons changesTherefore effective nuclear charge Therefore effective nuclear charge
increasesincreasesElectrons are pulled in tighterElectrons are pulled in tighterThe negative ions are larger than the The negative ions are larger than the
positive ions with the same number of positive ions with the same number of electrons.electrons.
Practice ProblemsPractice Problems
Arrange the following elements in order of Arrange the following elements in order of decreasing atomic radius:decreasing atomic radius:As, O, Sn, Ge, Ne, Ba, HeAs, O, Sn, Ge, Ne, Ba, He
Arrange the following elements in order of Arrange the following elements in order of increasing electronegativityincreasing electronegativityAl, Mg, P, Sr, O, F, RbAl, Mg, P, Sr, O, F, Rb
Ticket Out the DoorTicket Out the Door
Arrange the following elements in order of Arrange the following elements in order of increasing ionization energy:increasing ionization energy:Cs, Ba, Y, In, Ga, Si, P, FCs, Ba, Y, In, Ga, Si, P, F
Test Review ProblemTest Review Problem
Challenge ProblemChallenge ProblemPlace the following in order of increasing Place the following in order of increasing
size: Ne, Clsize: Ne, Cl--, Ar, Na, Ar, Na++
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