History of the Periodic History of the Periodic TableTable

Chapter 6Chapter 6

DobereinerDobereiner First person to create reasonably First person to create reasonably

accurate measurements for atomic accurate measurements for atomic mass.mass.

NewlandsNewlands In 1864, Newlands proposed an In 1864, Newlands proposed an

organization scheme for the elementsorganization scheme for the elements By arranging them in order of increasing By arranging them in order of increasing

atomic mass, he realized that their atomic mass, he realized that their properties repeated every eighth properties repeated every eighth element.element.

He called this periodicity the Law of He called this periodicity the Law of Octaves.Octaves.

Acceptance of his arrangement wasn’t Acceptance of his arrangement wasn’t immediate because it didn’t work immediate because it didn’t work universally in predicting chemical universally in predicting chemical properties.properties.

Meyer & MendeleevMeyer & Mendeleev

In 1869, Lothar Meyer demonstrated a In 1869, Lothar Meyer demonstrated a connection between atomic mass and elemental connection between atomic mass and elemental properties.properties.

In 1869, a Russian chemist named Dimitri In 1869, a Russian chemist named Dimitri Mendeleev also came up with a way of Mendeleev also came up with a way of organizing the elements that were known at the organizing the elements that were known at the time.time.

Both chemists set the elements out in order of Both chemists set the elements out in order of atomic massatomic mass

Both then grouped them into rows and columns Both then grouped them into rows and columns based on their chemical and physical properties. based on their chemical and physical properties.

Mendeleev predicted the existence and Mendeleev predicted the existence and properties of undiscovered elements, which is properties of undiscovered elements, which is largely why his table got such wide acceptance.largely why his table got such wide acceptance.

Mendeleev’s Early Periodic Mendeleev’s Early Periodic Table, Published in 1872Table, Published in 1872

MoseleyMoseley

Instead of ordering elements by total Instead of ordering elements by total atomic mass, order by proton atomic mass, order by proton (atomic) number.(atomic) number.

This creates some minor shufflings in This creates some minor shufflings in Mendeleev’s table and allows us to Mendeleev’s table and allows us to better predict unknown elements.better predict unknown elements.

The Modern Periodic TableThe Modern Periodic Table

Chapter 6Chapter 6

Arrangement and Arrangement and NomenclatureNomenclature

Rows are called periodsRows are called periods Columns are designated as groupsColumns are designated as groups Each column in the main table and each Each column in the main table and each

row at the bottom is also designated an row at the bottom is also designated an individual familyindividual family

Groups 1A, 2A, and 3-8A are the main Groups 1A, 2A, and 3-8A are the main groups, or representative elementsgroups, or representative elements

Groups 1B-8B are called the transition Groups 1B-8B are called the transition elementselements

The Periodic Table With Atomic Symbols, Atomic The Periodic Table With Atomic Symbols, Atomic

Numbers, and Partial Electron ConfigurationsNumbers, and Partial Electron Configurations

Broad Periodic Table Broad Periodic Table ClassificationsClassifications

Representative ElementsRepresentative Elements (main (main group): filling group): filling ss and and pp orbitals (Na, Al, orbitals (Na, Al, Ne, O)Ne, O)

Transition ElementsTransition Elements: filling : filling dd orbitals (Fe, Co, Ni)orbitals (Fe, Co, Ni)

Lanthanide and Actinide SeriesLanthanide and Actinide Series (inner transition elements): filling (inner transition elements): filling 44ff and and 55ff orbitals (Eu, Am, Es)orbitals (Eu, Am, Es)

Information Contained in Information Contained in the Periodic Tablethe Periodic Table

1.1. Each group member has the Each group member has the same valence electron same valence electron configuration (these configuration (these electrons primarily determine electrons primarily determine an atom’s chemistry).an atom’s chemistry).

2.2. The electron configuration of The electron configuration of any representative element.any representative element.

Information Contained in Information Contained in the Periodic Tablethe Periodic Table

3.3. Certain groups have special Certain groups have special names (alkali metals, alkaline names (alkali metals, alkaline earth metals, chalcogens, earth metals, chalcogens, halogens, etc).halogens, etc).

4.4. Metals and nonmetals are Metals and nonmetals are characterized by their chemical characterized by their chemical and physical properties.and physical properties.

Special Names Special Names for Groups in for Groups in the Periodic the Periodic TableTable

MetalsMetals Metals makeup more than 75% of the Metals makeup more than 75% of the

elements in the periodic table. Metals are elements in the periodic table. Metals are characterized by the following physical characterized by the following physical properties:properties:– They have metallic shine or luster.They have metallic shine or luster.– They are usually solids at room temperature.They are usually solids at room temperature.– They are malleable. Malleable means that They are malleable. Malleable means that

metals can be hammered, pounded, or pressed metals can be hammered, pounded, or pressed into different shapes without breaking. into different shapes without breaking.

– They are ductile meaning that they can be They are ductile meaning that they can be drawn into thin sheets or wires without breaking. drawn into thin sheets or wires without breaking.

– They are good conductors of heat and electricity.They are good conductors of heat and electricity.

Metals (cont)Metals (cont) All B and most A elements are metals.All B and most A elements are metals. The B The B At stairstep designates the border At stairstep designates the border

between metals and non-metalsbetween metals and non-metals 1A elements are alkali metals1A elements are alkali metals

– They are soft shiny metals that usually They are soft shiny metals that usually combine with group VIIA nonmetals in chemical combine with group VIIA nonmetals in chemical compounds in a 1:1 ratio.compounds in a 1:1 ratio.

2A elements are the alkaline earth metals2A elements are the alkaline earth metals– Both alkali and alkaline earth metals are Both alkali and alkaline earth metals are

chemically reactive, but 2A metals are less chemically reactive, but 2A metals are less reactive than 1As.reactive than 1As.

– They combine with the group VIIA nonmetals in They combine with the group VIIA nonmetals in a 1:2 ratio.a 1:2 ratio.

Transition Metals & Transition Metals & MetalloidsMetalloids

Transition metalsTransition metals– The remaining 1-8B elements are all The remaining 1-8B elements are all

transition elementstransition elements– The transition elements also have The transition elements also have

valence electrons in two shells instead valence electrons in two shells instead of one.of one.

Inner transition metalsInner transition metals– The lanthanide and actinide series The lanthanide and actinide series

comprise the inner transition metalscomprise the inner transition metals

MetalloidsMetalloids

Metalloids have characteristics of Metalloids have characteristics of both metals and nonmetals and so both metals and nonmetals and so can’t be classified as either, but can’t be classified as either, but something in between.something in between.– They are good conductors of heat and They are good conductors of heat and

electricityelectricity– They are not good conductors or They are not good conductors or

insulators.insulators. The six metalloids are B, Si, Ge, As, The six metalloids are B, Si, Ge, As,

Sb, and Te. Sb, and Te.

NonmetalsNonmetals

There are 17 nonmetals in the periodic There are 17 nonmetals in the periodic table, and they are characterized by four table, and they are characterized by four major physical properties.major physical properties.– They rarely have metallic luster.They rarely have metallic luster.– They are usually gases at room temperature.They are usually gases at room temperature.– Nonmetallic solids are neither malleable nor Nonmetallic solids are neither malleable nor

ductile. ductile. – They are poor conductors of heat and electricity.They are poor conductors of heat and electricity.

The elements above the B The elements above the B At stairstep At stairstep are nonmetalsare nonmetals

Nonmetals (cont)Nonmetals (cont) Group 6A contains the chalcogen elementsGroup 6A contains the chalcogen elements Group 7A contains the highly reactive halogen Group 7A contains the highly reactive halogen

elementselements– They are fluorine, chlorine, bromine, and iodine. They are fluorine, chlorine, bromine, and iodine. – The halogens exist as diatomic molecules in nature.The halogens exist as diatomic molecules in nature.

Group 8A comprises the completely non-reactive Group 8A comprises the completely non-reactive noble gasesnoble gases– The noble gases are also called rare gas elements, and The noble gases are also called rare gas elements, and

they all occur in nature as gases. they all occur in nature as gases. – The noble gases fulfill the octet rule by having a full The noble gases fulfill the octet rule by having a full

outer level with 8 valence electrons. outer level with 8 valence electrons. – Therefore, they do not undergo chemical reactions Therefore, they do not undergo chemical reactions

because they do not accept any electrons.because they do not accept any electrons.

Valence Electrons and the Valence Electrons and the Periodic TablePeriodic Table

Valence Electrons and GroupValence Electrons and Group– Atoms in the same group have the same Atoms in the same group have the same

chemical properties because they have the chemical properties because they have the same number of valence electrons.same number of valence electrons.

– Moreover, they have the same outermost Moreover, they have the same outermost orbital structureorbital structure E.g. 1A elements all have sE.g. 1A elements all have s1 1 valence electronsvalence electrons E.g. 2A elements all have sE.g. 2A elements all have s22 valence electrons valence electrons

Valence Electrons and PeriodValence Electrons and Period– The primary quantum number (n) for an The primary quantum number (n) for an

element’s valence electrons is the same its element’s valence electrons is the same its period.period. E.g. Lithium’s valence electron is n=2 and Li is found E.g. Lithium’s valence electron is n=2 and Li is found

in the 2in the 2ndnd period period

The Octet RuleThe Octet Rule

Atoms tend to lose, gain, or share Atoms tend to lose, gain, or share electrons until they are surrounded electrons until they are surrounded by 8 valence electronsby 8 valence electrons