The Periodic LawThe Periodic Law

Electron Configuration and Electron Configuration and Periodic PropertiesPeriodic Properties

What do we already know?What do we already know?

Elements are arranged in the Elements are arranged in the periodic table by atomic number.periodic table by atomic number.

Rough correlation between element Rough correlation between element arrangement and electron arrangement and electron configuration.configuration.

More relationships between periodic More relationships between periodic law and electron configurations.law and electron configurations.

Atomic RadiiAtomic Radii

Atomic radius may be defined as one-half Atomic radius may be defined as one-half the distance between the nuclei of the distance between the nuclei of identical atoms that are bonded together.identical atoms that are bonded together.

In general, atomic radii decrease from left In general, atomic radii decrease from left to right across a period and increase to right across a period and increase down a group. down a group.

The trend to smaller atoms across a period The trend to smaller atoms across a period is caused by increasing + charge of the is caused by increasing + charge of the nucleus.nucleus.

Atomic Radii TrendsAtomic Radii Trends

Ionization EnergyIonization Energy

An ion is an atom that has a + or – charge.An ion is an atom that has a + or – charge. Any process that results in the formation Any process that results in the formation

of an ion is referred to as ionization.of an ion is referred to as ionization. First ionization energies increase across a First ionization energies increase across a

period and decrease down a group.period and decrease down a group. The energy required to remove one The energy required to remove one

electron from a neutral atom is the electron from a neutral atom is the ionization energy (kJ/mol).ionization energy (kJ/mol).

Ionization EnergyIonization Energy

Group 1 Elements have relativelysmall ionization energies because they do not require much energy todetach one electron.

Na – 496 kJ/mol

Ionization Energy vs. ZIonization Energy vs. Z

Electron AffinityElectron Affinity

Energy change resulting from the Energy change resulting from the addition of an electron is electron addition of an electron is electron affinity.affinity.

The halogens have high electron The halogens have high electron affinities because the addition of an affinities because the addition of an electron to an atom results in a electron to an atom results in a completely filled shell.completely filled shell.

The noble gases have electron affinities The noble gases have electron affinities of zero.of zero.

Electron AffinityElectron Affinity

Electron affinity tends to increase Electron affinity tends to increase across a period.across a period.

Some irregularities due to extra Some irregularities due to extra stability of half or filled sublevels. stability of half or filled sublevels.

Electron affinity tends to decrease Electron affinity tends to decrease down a group. down a group.

Added electrons are farther from the Added electrons are farther from the nucleusnucleus

Electron AffinityElectron Affinity

ElectronegativityElectronegativity Electronegativity is a measure of the ability of Electronegativity is a measure of the ability of

an atom in a chemical compound to attract an atom in a chemical compound to attract electrons.electrons.

Electronegativities tend to increase across Electronegativities tend to increase across each period, or decrease down a group.each period, or decrease down a group.

Elements with high ionization energies have Elements with high ionization energies have high electronegativities due to the strong pull high electronegativities due to the strong pull exerted on electrons by the nucleus. exerted on electrons by the nucleus.

Ionic RadiiIonic Radii

A positive ion is known as a cation.A positive ion is known as a cation. The formation of a cation by the loss The formation of a cation by the loss

of electrons leads to a decrease in of electrons leads to a decrease in radius.radius.

A negative ion is known as an anion.A negative ion is known as an anion. The formation of an anion by the The formation of an anion by the

addition of electrons always leads to addition of electrons always leads to an increase in atomic radius.an increase in atomic radius.

Valence ElectronsValence Electrons

The electrons available to be lost, The electrons available to be lost, gained, or shared in the formation of gained, or shared in the formation of chemical compounds are referred to chemical compounds are referred to as valence electrons.as valence electrons.

Main-groups elements valence Main-groups elements valence electrons correspond to their group electrons correspond to their group configuration, i.e. Group 1 – 1 configuration, i.e. Group 1 – 1 valence, 2-2, 13-3, 14-4, etc.valence, 2-2, 13-3, 14-4, etc.

Summary of Major TrendsSummary of Major Trends Moving Left --> Right.Moving Left --> Right.

Atomic Radius Decreases Atomic Radius Decreases Ionic Radius DecreasesIonic Radius Decreases Ionization Energy Increases Ionization Energy Increases Electron Affinity IncreasesElectron Affinity Increases Electronegativity Increases Electronegativity Increases

Moving Top --> Bottom. Moving Top --> Bottom. Atomic Radius Increases Atomic Radius Increases Ionic Radius IncreasesIonic Radius Increases Ionization Energy Decreases Ionization Energy Decreases Electron Affinity DecreasesElectron Affinity Decreases Electronegativity Decreases Electronegativity Decreases