PeriodicityPeriodicity

And the Periodic TableAnd the Periodic Table

The Big IdeaThe Big Idea

• Periodic trends in the properties of Periodic trends in the properties of atoms allow us to predict physical atoms allow us to predict physical and chemical propertiesand chemical properties

Development of the Development of the Periodic TablePeriodic Table

• The periodic table evolved over The periodic table evolved over time as scientists discovered more time as scientists discovered more useful ways to compare and useful ways to compare and organize the elementsorganize the elements

The Periodic TableThe Periodic Table

• Mendeleev (1869) – first periodic Mendeleev (1869) – first periodic tabletable

• Based on increasing atomic mass Based on increasing atomic mass and repeating properties of and repeating properties of elementselements

• Had spaces for “missing” elements Had spaces for “missing” elements he predictedhe predicted

Henry MoseleyHenry Moseley

• Discovered in 1914 Discovered in 1914 that elements’ that elements’ properties more properties more closely followed closely followed their atomic their atomic numbernumber

• Modern Periodic Modern Periodic Table based on Table based on this discoverythis discovery

Periodic LawPeriodic Law

• Physical and chemical properties of Physical and chemical properties of elements are periodic functions of elements are periodic functions of atomic numbersatomic numbers

Classification of the Classification of the ElementsElements

• Elements are organized into Elements are organized into different blocks in the periodic different blocks in the periodic table according to their electron table according to their electron configurationsconfigurations

Organizing the Elements Organizing the Elements by Electron Configurationby Electron Configuration

• Electrons in the highest principal energy level are called valence electrons.

• All group 1 elements have one valence electron.

Organizing the Elements Organizing the Elements by Electron Configurationby Electron Configuration

• The energy level of an element’s valence electrons indicates the period on the periodic table in which it is found.

• The number of valence electrons for elements in groups 13-18 is ten less than their group number.

Organizing the Elements Organizing the Elements by Electron Configurationby Electron Configuration

What is periodicity?What is periodicity?

• Properties of the elements change in a Properties of the elements change in a predictable way as you move through predictable way as you move through the periodic tablethe periodic table

• These properties includeThese properties include– Atomic radiusAtomic radius– Octet RuleOctet Rule– Ionic radiusIonic radius– Ionization energyIonization energy– ElectronegativityElectronegativity

How are the elements How are the elements organized?organized?

• Periodic Table: a complete chart of Periodic Table: a complete chart of all elements in the universeall elements in the universe

• Arranged according to physical and Arranged according to physical and chemical propertieschemical properties

• Each box on the table contains the Each box on the table contains the atomic number, atomic mass, and atomic number, atomic mass, and chemical symbolchemical symbol

How are the elements How are the elements organized?organized?

• Groups: also known as families; Groups: also known as families; are the columnsare the columns

• Have similar propertiesHave similar properties• Some have specific names:Some have specific names:

– Family 1: Alkali MetalsFamily 1: Alkali Metals– Family 2: Alkaline Earth MetalsFamily 2: Alkaline Earth Metals– Families 3 – 12: Transition MetalsFamilies 3 – 12: Transition Metals– Family 13: Boron FamilyFamily 13: Boron Family

How are the elements How are the elements organized?organized?

– Family 14: Carbon FamilyFamily 14: Carbon Family– Family 15: Nitrogen FamilyFamily 15: Nitrogen Family– Family 16: Oxygen FamilyFamily 16: Oxygen Family– Family 17: Halogen FamilyFamily 17: Halogen Family– Family 18: Noble GasesFamily 18: Noble Gases

• Periods: the rows on the periodic Periods: the rows on the periodic tabletable– Do not have similar propertiesDo not have similar properties

The Modern Periodic TableThe Modern Periodic Table

MetalsMetals

• To the left of the stair-step lineTo the left of the stair-step line• 88 elements88 elements• Tend to lose electronsTend to lose electrons• Most reactive in the s blockMost reactive in the s block• Includes alkali metals and Includes alkali metals and

alkaline earth metalsalkaline earth metals

Properties of MetalsProperties of Metals

• Shiny lusterShiny luster• Good conductors of heatGood conductors of heat• Good conductors of electricityGood conductors of electricity• Usually solids at room tempUsually solids at room temp• MalleableMalleable• DuctileDuctile

goldlead

nickel copper

NonmetalsNonmetals

• On right side of stair-step lineOn right side of stair-step line• Tend to gain electronsTend to gain electrons• Most reactive group is halogensMost reactive group is halogens• Least reactive is Noble gasesLeast reactive is Noble gases

Properties of NonmetalsProperties of Nonmetals

• Dull lusterDull luster• Poor conductors of heatPoor conductors of heat• Poor conductors of electricityPoor conductors of electricity• BrittleBrittle• Many are gases at room tempMany are gases at room temp

bromine

Carbon (graphite)

sulfur

MetalloidsMetalloids

• On either side of stair-step lineOn either side of stair-step line• Have properties of metals and Have properties of metals and

nonmetalsnonmetals• Includes all elements that touch Includes all elements that touch

the line except Al and Pothe line except Al and Po• Many are used in transistorsMany are used in transistors

antimony

germanium

Alkali MetalsAlkali Metals

• Group 1 (except H)Group 1 (except H)• All have only 1 valence electronAll have only 1 valence electron• Most reactive metals; never found Most reactive metals; never found

in pure state in naturein pure state in nature• Soft, shiny, have relatively low Soft, shiny, have relatively low

melting pointsmelting points

Alkaline Earth MetalsAlkaline Earth Metals

• Group 2Group 2• All have 2 valence electronsAll have 2 valence electrons• Are the second most reactive metals; Are the second most reactive metals;

never found naturally in pure statenever found naturally in pure state• Harder, denser, stronger than alkali Harder, denser, stronger than alkali

metalsmetals• Have higher melting points than alkali Have higher melting points than alkali

metalsmetals

Transition MetalsTransition Metals

• Groups 3 – 12Groups 3 – 12• All have 1 or 2 valence electrons All have 1 or 2 valence electrons

(in s sublevels)(in s sublevels)• Do not fit into any other group or Do not fit into any other group or

familyfamily• Have many irregularities in their Have many irregularities in their

electron configurationselectron configurations

Boron FamilyBoron Family

• Group 13Group 13• Have 3 valence electronsHave 3 valence electrons• Boron is a metalloid, while all of the Boron is a metalloid, while all of the

others are metalsothers are metals

Carbon FamilyCarbon Family

• Group 14Group 14• All have four valence electronsAll have four valence electrons• Carbon is a nonmetal; Si and Ge Carbon is a nonmetal; Si and Ge

are metalloids; Sn and Pb are are metalloids; Sn and Pb are metalsmetals

Nitrogen FamilyNitrogen Family

• Group 15Group 15• All have 5 valence electrons (in s All have 5 valence electrons (in s

and p sublevels)and p sublevels)• N and P are nonmetals; As and Sb N and P are nonmetals; As and Sb

are metalloids; Bi is a metalare metalloids; Bi is a metal

Oxygen FamilyOxygen Family

• Group 16Group 16• All have 6 valence electrons (in s All have 6 valence electrons (in s

and p sublevels)and p sublevels)• All are nonmetals except Te, which All are nonmetals except Te, which

is a metalloid, and Po, which is a is a metalloid, and Po, which is a metal.metal.

HalogensHalogens

• Means “salt former”Means “salt former”• Group 17Group 17• All have 7 valence electrons (in s All have 7 valence electrons (in s

and p sublevels)and p sublevels)• Most reactive nonmetalsMost reactive nonmetals• All are nonmetals except At, which All are nonmetals except At, which

is a metalloidis a metalloid

Noble GasesNoble Gases

• Group 18Group 18• Complete, stable electron Complete, stable electron

configuration (no valence configuration (no valence electrons)electrons)

• Most unreactive elementsMost unreactive elements

Rare Earth ElementsRare Earth Elements

• Found in 2 rows at bottom of Periodic Found in 2 rows at bottom of Periodic TableTable

• Also known as the inner transition Also known as the inner transition metalsmetals

• Lanthanide series: starts with LaLanthanide series: starts with La• Actinide series: starts with AcActinide series: starts with Ac• Little variation in propertiesLittle variation in properties• Actinides are radioactive; only first three Actinides are radioactive; only first three

and Pu are found in nature and Pu are found in nature

Periodic TrendsPeriodic Trends

• Trends among elements in the Trends among elements in the periodic table include their size and periodic table include their size and their ability to lose or attract their ability to lose or attract electronselectrons

Atomic RadiusAtomic Radius

• For elements that occur as molecules, the atomic radius is half the distance between nuclei of identical atoms.

Atomic RadiusAtomic Radius

Atomic RadiusAtomic Radius

• Atomic radius generally increases as you move down a group.

• The outermost orbital size increases down a group, making the atom larger.

Ionic RadiusIonic Radius

• An ion is an atom or bonded group of atoms with a positive or negative charge.

• When atoms lose electrons and form positively charged ions, they always become smaller for two reasons:

1. The loss of a valence electron can leave an empty outer orbital resulting in a small radius.

2. Electrostatic repulsion decreases allowing the electrons to be pulled closer to the radius.

Ionic RadiusIonic Radius

• When atoms gain electrons, they can become larger, because the addition of an electron increases electrostatic repulsion.

Ionic RadiusIonic Radius

Ionic RadiusIonic Radius

• The ionic radii of positive ions generally decrease from left to right.

• The ionic radii of negative ions generally decrease from left to right, beginning with group 15 or 16.

Ionization EnergyIonization Energy

• The energy needed to remove one of its The energy needed to remove one of its electronselectrons

• Decreases as you move down a groupDecreases as you move down a group• Increases as you move across a periodIncreases as you move across a period• Successive ionization energies increase Successive ionization energies increase

for every electron removedfor every electron removed

Ionization EnergyIonization Energy

Octet Rule (Rule of 8)Octet Rule (Rule of 8)

• Atoms tend to gain, share, or lose Atoms tend to gain, share, or lose in order to acquire a full set of in order to acquire a full set of valence electrons (in most cases, valence electrons (in most cases, this is 8)this is 8)

ElectronegativityElectronegativity

• Reflects an atom’s ability to attract Reflects an atom’s ability to attract electrons in a chemical bondelectrons in a chemical bond

• Related to its ionization energy and Related to its ionization energy and electron affinityelectron affinity

• Increases as you move across a periodIncreases as you move across a period• Increases as you move up a groupIncreases as you move up a group

ElectronegativityElectronegativity