Chapter 8

Chapter 8Periodic Properties of the ElementsPeriodic Properties/TrendsWhy would we care about the various trends and properties we observe throughout the periodic table?Mendeleevs Periodic Table

Mendeleevs Periodic TableArranged the 65 known elements by atomic mass and by recurrence of various physical and chemical properties.The Periodic Table today is very similar but arranged according to atomic number (number of protons).The arrangement led to families of elements with similar properties and at the time allowed for the prediction and properties of elements yet to be discovered.

Eletronic Energy Levels

Electron ConfigurationsFilling order:Lowest energy orbitals are filled firstOnly two electrons are allowed in each orbitalEach electron has a different spinWhen filling sublevels, fill each orbital with a single electron first, then go back and spin pair with a second electron when necessaryPauli Exclusion PrincipleNo two electrons in the same atom can have the same four quantum numbersSince the first three quantum numbers define the orbital, this means only two electrons can be in the same orbital and they must have opposite spins.Quantum Numbers - RecapNameSymbolPermitted ValuesPropertiesprincipalnpositive integersorbital energy (size)angular momentumlintegers from 0 to n-1orbital shapemagneticmlintegers from l to +lorbital orientationspinms+1/2 or -1/2direction of e- spinHunds RuleElectrons pair only after each orbital in a subshell is occupied by a single electron.Helium

10Carbon

11Orbital Diagrams

ExampleWrite a set of quantum numbers for the third electron and a set for the eighth electron of the F atom.Orbital Occupancy

Some Outer e- Configurations

Orbital EnergiesThe Effect of Nuclear Charge, ZeffHigher nuclear charge lowers orbital energy (stabilizes the system) by increasing nucleus-electron attractions.The Effect of Electron Repulsions (Shielding)Additional electron in the same orbitalMakes less stableAn additional electron raises the orbital energy through electron-electron repulsions.Additional electrons in inner orbitals Makes outer orbital less stableInner electrons shield outer electrons more effectively than do electrons in the same sublevel.

Adding an e- to the Same Orbital

Other e- in Inner Orbitals

18Orbital Shape

Radial Distribution

Radial Probability

Shielding and Penetration

Energy Order

Filling Order

Filling Order

Valence Electrons

Valence Electrons

Electron Configuration of IonsCations formed when electrons are removed from the highest energy occupied orbitalAnions formed when electrons are added to the lowest energy unoccupied orbitalTransition metals the highest ns electrons are removed first, even though they are not the last added28Electron Configuration of Ions

Electron Configuration of Ions

Magnetic PropertiesParamagnetic: electron configurations that result in unpaired electrons mean that the atom or ion will have a net magnetic fieldWill be attracted to a magnetic fieldDiamagnetic: electron configurations that result in all paired electrons mean that the atom or ion will have no magnetic field Slightly repelled by a magnetic fieldMagnetic Properties

Magnetic PropertiesCan we predict electron configuration from magnetic data?Nickel is diamagnetic and palladium is paramagnetic. What can you conclude about their electron structures based on this data?Cd+2 is diamagnetic. Based on this information, which electrons are lost from cadmium when it ionizes?Periodic PropertiesAtomic sizeEffective nuclear chargeIonization energyElectron affinityMetallic Character34Atomic Size

Atomic Size

Atomic Size

Atomic SizeAtomic Size39Atomic Size

Ionic RadiiCations radius decreases due to an increase in ZeffAnions radius increases due to crowding of more electrons into shell41Ionic Radii42Ionic Radii - Cations43Ionic Radii - Anions44

Relating Sizes4545Figure: 12-07

Title:Formation of Na+ and Cl- Ions

Caption:The radius of the sodium atom decreases, while the chloride atom increases when ionized.

Notes:Losing an electron means that the positive nucleus can pull the other electrons in more strongly. Gaining an electron means that the positive nucleus is less effective in pulling the electrons in.Effective Nuclear Charge, ZeffThe amount of positive charge on the nucleus felt by an electronElectrons in between the nucleus and outer electrons sheild the outer electrons from feeling the full force of positive charge coming from the nucleus46Effective Nuclear Charge47Effective Nuclear Charge

Effective Nuclear Charge

Ionization EnergyThe amount of energy required to remove the outermost electron from an isolated neutral atom in the gaseous state50Ionization Energy

Ionization Energy

Ionization Energy53Ionization Energy54Ionization EnergyALWAYS increases as you pull off more electronsTakes a huge leap when an electron is removed from a new inner shell55Exceptions

ExampleName the Period 3 element with the following ionization energies (in kJ/mol) and write its electron configuration:IE1IE2IE3IE4IE5IE61012190329104956627822,230Electron AffinityThe energy change that occurs when an electron is added to an atom (or ion) in the gaseous stateFrequently costs nothing, but actually yields energyTherefore, EAs are usually negative58Electron Affinity59Electron Affinity

Metallic Character61Metallic Character62Recap

Descriptive ChemistryAlkali MetalsAlkaline Earth MetalsHalogensNobel Gases

6565

6666Figure: 08-20-01UN

Title: Chlorine, Bromine, Iodine

Caption: The most commonly encountered halogens.

6767Figure: 08-20

Title: Reactions of the Alkali Metals with Water

Caption: The reaction becomes progressively more vigorous as you move down the group.

6868Figure: 08-T04

Title: TABLE 8.4 Properties of the Noble Gases

Caption: The listed properties show several trends that can be explained by chemistry.