CH 6CH 6The Periodic Table and The Periodic Table and

Periodic TrendsPeriodic Trends

Organizing the ElementsOrganizing the Elements

Mendeleev arranged the elements in his Mendeleev arranged the elements in his periodic table in order of increasing atomic periodic table in order of increasing atomic massmass18691869

The Periodic LawThe Periodic LawWhen the elements are arranged in order When the elements are arranged in order

of increasing atomic number, there is a of increasing atomic number, there is a periodic repetition of their physical and periodic repetition of their physical and chemical propertieschemical properties

Periods and GroupsPeriods and GroupsPeriods – rows on a periodic tablePeriods – rows on a periodic tableGroups – columns on a periodic tableGroups – columns on a periodic table

The Periodic TableThe Periodic TableDisplays symbols and names of the Displays symbols and names of the

elementselements Information about the structure of the atomInformation about the structure of the atomAverage atomic massAverage atomic massAtomic numberAtomic number

MetalsMetalsGood conductors of electricity and heatGood conductors of electricity and heatLusterLusterDuctileDuctileMalleableMalleable

NonmetalsNonmetalsPoor conductors of heat and electricityPoor conductors of heat and electricityBrittleBrittleVaries in states (solids, liquids, gases)Varies in states (solids, liquids, gases)

MetalloidsMetalloidsAlong the stair-stepAlong the stair-stepProperties similar to those of metals and Properties similar to those of metals and

nonmetalsnonmetalsConduct heat and electricity somewhatConduct heat and electricity somewhat

http://chemlab.pc.maricopa.edu/periodic/default.html

Important RegionsImportant RegionsAlkali metals – Group 1AAlkali metals – Group 1AAlkaline earth metal – Group 2AAlkaline earth metal – Group 2AHalogens – Group 7AHalogens – Group 7ANoble gases – Group 8ANoble gases – Group 8A

Transition metalsTransition metals Inner Transition metalsInner Transition metals

LanthanidesLanthanidesActinidesActinides

Electron Configurations Electron Configurations in Groupsin Groups

Elements can be sorted into noble gases, Elements can be sorted into noble gases, representative elements, transition metals, representative elements, transition metals, inner transition metals based on their inner transition metals based on their electron configurationselectron configurationsEvery element ends in the same last term in Every element ends in the same last term in

the electron configurationthe electron configuration

Representative ElementsRepresentative Elements

Groups 1,2,13,14,15,16,17Groups 1,2,13,14,15,16,17Called representative elements because Called representative elements because

they display a wide range of physical and they display a wide range of physical and chemical propertieschemical properties

Transition ElementsTransition Elements

In atoms of a transition metal, the highest In atoms of a transition metal, the highest occupied s sublevel and a nearby d occupied s sublevel and a nearby d sublevel contain electrons. sublevel contain electrons.

These elements are characterized by the These elements are characterized by the presence of electrons in the d orbitalspresence of electrons in the d orbitals

Inner transition elements contain unfilled f Inner transition elements contain unfilled f orbitalsorbitals

Periodic TrendsPeriodic TrendsAtomic radius – ½ the distance between Atomic radius – ½ the distance between

the nuclei of two atoms of the same the nuclei of two atoms of the same element when the atoms are joinedelement when the atoms are joinedExtremely small – measured in picometersExtremely small – measured in picometers

Atomic size (radius) increases from top to Atomic size (radius) increases from top to bottom within a group and decreases from bottom within a group and decreases from left to right across a period.left to right across a period.

Periodic TrendsPeriodic TrendsAtomic radius – WHY???Atomic radius – WHY???

Group trends – as the atomic number Group trends – as the atomic number increases within a group, the charge on the increases within a group, the charge on the nucleus increases and the number of nucleus increases and the number of occupied energy levels increases. occupied energy levels increases. The increase in positive charge draws the The increase in positive charge draws the

electrons closer to the nucleuselectrons closer to the nucleusThe increase in the number of occupied The increase in the number of occupied

orbitals shields the electrons in the highest orbitals shields the electrons in the highest occupied energy level from the attraction of the occupied energy level from the attraction of the protons in the nucleus.protons in the nucleus.

Periodic TrendsPeriodic TrendsAtomic Size – WHY????Atomic Size – WHY????

Periodic trends – each element has one more Periodic trends – each element has one more proton and one more electron that then proton and one more electron that then preceding element.preceding element.Across a period, the electrons are added to the Across a period, the electrons are added to the

same principal energy level. The shielding same principal energy level. The shielding effect is constant for all the elements in a effect is constant for all the elements in a periodperiod

The increasing nuclear charge pulls the The increasing nuclear charge pulls the electrons in the highest occupied energy level electrons in the highest occupied energy level closer to the nucleus and the atomic size closer to the nucleus and the atomic size decreasesdecreases

IonsIonsPositive and negative ions form when Positive and negative ions form when

electrons are transferred between atoms\electrons are transferred between atoms\Metals form cations – they lose electrons Metals form cations – they lose electrons

to form a positive chargeto form a positive chargeNonmetals form anions – they gain Nonmetals form anions – they gain

electrons to form a negative chargeelectrons to form a negative charge

Periodic TrendsPeriodic Trends Ionization Energy – the energy required to Ionization Energy – the energy required to

remove an electron from an atomremove an electron from an atomMeasured in the gaseous stateMeasured in the gaseous stateThe energy required to remove the first The energy required to remove the first

electron – first ionization energyelectron – first ionization energyThe energy required to remove the second The energy required to remove the second

electron – second ionization energyelectron – second ionization energyThe energy required to remove the third The energy required to remove the third

electron – third ionization energyelectron – third ionization energy

Periodic TrendsPeriodic Trends Ionization EnergyIonization Energy

Can help you predict what ions will formCan help you predict what ions will form

The first ionization energy tends to The first ionization energy tends to decrease from top to bottom within a decrease from top to bottom within a group and increase from left to right group and increase from left to right across a periodacross a period

Periodic TrendsPeriodic Trends Ionization Energy – WHY????Ionization Energy – WHY????

Atomic size increases as the atomic number Atomic size increases as the atomic number increases within a group. As the size of the increases within a group. As the size of the atom increases, nuclear charge has a smaller atom increases, nuclear charge has a smaller effect on the electrons in the highest occupied effect on the electrons in the highest occupied energy level. So less energy is required to energy level. So less energy is required to remove an electronremove an electron

Periodic TrendsPeriodic Trends Ionization Energy – WHY????Ionization Energy – WHY????

The nuclear charge increases across the The nuclear charge increases across the period, but the shielding effect remains period, but the shielding effect remains constant. So there is an increase in the constant. So there is an increase in the attraction of the nucleus for an electron. attraction of the nucleus for an electron. Thus, it takes more energy to remove an Thus, it takes more energy to remove an electron from an atomelectron from an atom

Periodic TrendsPeriodic Trends Ionic Size Ionic Size

Cations are always smaller than the atoms Cations are always smaller than the atoms from which they formfrom which they form

Anions are always larger than the atoms from Anions are always larger than the atoms from which they formwhich they form

Periodic TrendsPeriodic TrendsElectronegativity – the ability of an atom of Electronegativity – the ability of an atom of

an element to attract electrons when the an element to attract electrons when the atom is in a compoundatom is in a compound

Periodic TrendsPeriodic TrendsElectronegativity – decrease from top to Electronegativity – decrease from top to

bottom within a group. For representative bottom within a group. For representative elements, the values tend to increase from elements, the values tend to increase from left to right across a periodleft to right across a period

Metals have low valuesMetals have low valuesNonmetals have higher valuesNonmetals have higher valuesFluorine – highest with value of 4Fluorine – highest with value of 4

Summary of TrendsSummary of Trends