PeriodicityPeriodicity

Dr. Ron RusayDr. Ron Rusay

Atomic Structure and Periodicity

The History of the Periodic Table The Aufbau Principles and the Periodic Table Periodic Trends in Atomic Properties The Properties of a Group: The Alkali Metals

Types of Chemical Bonds Electronegativity Bond Polarity and Dipole Moments Ions: Electron Configurations and Sizes Formation of Binary Ionic Compounds

Periodic TablePeriodic Table1

• Mendeleev’s Table 1868-1871Mendeleev’s Table 1868-1871Mural at St.Petersburg University, RussiaMural at St.Petersburg University, Russia

Periodic PropertiesPeriodic Properties

Calibrated Peer Review Writing AssignmentCalibrated Peer Review Writing Assignment

Chemical BondsChemical Bonds

Definition:Definition:Attractive forces which hold atoms Attractive forces which hold atoms

together and provide a particular together and provide a particular molecular arrangement of atoms molecular arrangement of atoms with new chemical properties.with new chemical properties.

Electron Configurations & Bonds Electron Configurations & Bonds Noble Gases and The Rule of EightNoble Gases and The Rule of Eight

When twoWhen two nonmetals nonmetals react to form react to form a covalent bond: They a covalent bond: They share share electrons electrons to achieve a Noble gas electron to achieve a Noble gas electron configuration.configuration.

When aWhen a nonmetalnonmetal and aand a metal metal react to form an ionic compound: react to form an ionic compound: Valence electrons of the Valence electrons of the metalmetal are are lostlost and the and the nonmetal gainsnonmetal gains these electrons. these electrons.

Ionic BondsIonic Bonds

Result from electrostatic attractions of Result from electrostatic attractions of closely packed, closely packed, oppositely charged oppositely charged ionsions..

Form when an atom which can easily Form when an atom which can easily lose electrons lose electrons reacts with one which reacts with one which has a has a high electron affinityhigh electron affinity, that is, it can , that is, it can easily gain electrons.easily gain electrons.

Eg. Mg and Cl; K and OEg. Mg and Cl; K and O

Ionic vs. Covalent BondingIonic vs. Covalent Bonding

Bond LengthBond Length(Covalent Bonds)(Covalent Bonds)

Interatomic Interatomic distance.distance. It is the distance where the It is the distance where the

bond energy is at a minimum value, bond energy is at a minimum value, and which is the most stable atomic and which is the most stable atomic form.form.

Bond Lengths and Covalent Radius

Periodic TrendsPeriodic TrendsAtomic RadiusAtomic Radius

Atomic RadiiAtomic Radii::What’s a picometer?What’s a picometer?

1 x 10 1 x 10 -12 -12 mm

decreasesdecreases going from left to right going from left to right across a across a periodperiod;;

increases increases going down a going down a groupgroup..

Atomic RadiiAtomic Radii

QUESTIONQUESTION

ANSWERANSWER

2+

D) Mg

The loss of electrons will always decrease the size of the ion and the addition of electrons will always increase the size of the ion.

Ionization EnergyIonization Energy

QUESTIONQUESTION

ANSWERANSWER .

C) greater than 735 kJ/mol

The second ionization energy is always greater than the first, because the next electron is no longer leaving a neutral atom, but one with a +1 charge.

Periodic TrendsPeriodic Trends

First ionization energyFirst ionization energy: : increases increases from left to right from left to right

across a across a PeriodPeriod;;

decreasesdecreases going down a going down a GroupGroup..

QUESTIONQUESTION

ANSWERANSWER

D) S

Ionization energy increases moving up a group and moving right along a row.

Electron AffinityElectron Affinity The energy change associated The energy change associated

with the addition of an electron to a with the addition of an electron to a gaseous gaseous atomatom..

X(g) + eX(g) + e X X(g)(g)

ElectronegativityElectronegativity

The ability of an atom in a The ability of an atom in a molecule to attract shared electrons molecule to attract shared electrons to itself.to itself.

= (H = (H X) X)actualactual (H (H X) X)expectedexpected

ElectronegativityElectronegativity

ElectronegativityElectronegativity

QUESTIONQUESTION

ANSWERANSWER .

B) Rb < O < F

Electronegativities increase moving up a column and to the right in the periodic table.

QUESTIONQUESTION

ANSWERANSWER .

D) ionic bonds

If two atoms have greatly differing electronegativities the more electronegative atom will pull on the bonding electrons so strongly the electrons will transfer from one atom to the other.

Covalent Bond PolarityCovalent Bond Polarity

A molecule, such as HF, that has a A molecule, such as HF, that has a center of positive charge and a center of center of positive charge and a center of negative charge is said to be negative charge is said to be polarpolar, or to have , or to have a a dipole momentdipole moment..δ+ δ−FH

QUESTIONQUESTION

ANSWERANSWER

B) KF

Use the periodic table or an electronegativity chart to determine the greatest difference in electronegativities of atoms in the binary ionic compounds.

Trends in ReactivityTrends in ReactivityLithium (Li), Sodium (Na) & Potassium (K)Lithium (Li), Sodium (Na) & Potassium (K)

•What might account for this trend? What might account for this trend? •Do you expect the Alkaline Earths Do you expect the Alkaline Earths (Group IIA) to behave similarly?(Group IIA) to behave similarly?•Does this trend apply to all Groups?Does this trend apply to all Groups?

What is trend in the What is trend in the chemical reactivity chemical reactivity observed for the observed for the alkali metals, Group alkali metals, Group IA?IA?

Transition Metals Transition Metals (B Group Elements)(B Group Elements)

Transition Metals (B Groups) Transition Metals (B Groups) Oxidation StatesOxidation States

Information & the Periodic TableInformation & the Periodic Table

A great deal of specific, general and comparative A great deal of specific, general and comparative information can be developed from the Periodic information can be developed from the Periodic Table:Table:

1.1. Group valence electron configurations. Group valence electron configurations. 2.2. Individual electron configurations.Individual electron configurations. 3.3. General chemical behavior and General chemical behavior and

physical properties.physical properties. 4.4. Distinguishing metals and nonmetals.Distinguishing metals and nonmetals.

Summary of Periodic TrendsSummary of Periodic Trends Periods (Horizontal Rows)Periods (Horizontal Rows)

Atomic sizeAtomic size generally decreases across a generally decreases across a Period.Period.

The The first ionization energyfirst ionization energy and and electronegativityelectronegativity generally increase across generally increase across a Period..a Period..

This is a result of This is a result of increasing effective nuclear increasing effective nuclear chargecharge and electrons being in the and electrons being in the same same principal energyprincipal energy level. level.

Summary of Periodic TrendsSummary of Periodic TrendsPeriods (Horizontal Rows)Periods (Horizontal Rows)

Metallic character decreases as elements Metallic character decreases as elements change from metals to metalloids to change from metals to metalloids to nonmetals.nonmetals.

General reactivity is highest at the left and General reactivity is highest at the left and right ends of a Period. (Excluding the inert right ends of a Period. (Excluding the inert noble gases.)noble gases.)

In Period 2, the physical properties change In Period 2, the physical properties change abruptly between carbon (solid) and abruptly between carbon (solid) and nitrogen (gas).nitrogen (gas).