History of the Periodic History of the Periodic TableTable

Antoine LavoisierAntoine Lavoisier

In the late 1790s, In the late 1790s, he compiled a list he compiled a list of the known of the known elements at the elements at the time.time.

This list contained This list contained 2323 elements. elements.

1743 - 1794

But times were about to change…But times were about to change…

In the 1800’s, there were many In the 1800’s, there were many changes in the worldchanges in the world• ElectricityElectricity• SpectrometerSpectrometer• Industrial RevolutionIndustrial Revolution

As a result, there was an increase in As a result, there was an increase in the number of known elementsthe number of known elements• By the 1870, there were By the 1870, there were 7070 known known

elementselements

An agreement is reached…An agreement is reached…

Then in the 1860’s, chemists agreed Then in the 1860’s, chemists agreed upon a method for accurately upon a method for accurately determining the determining the atomic massatomic mass of of elements.elements.

John NewlandsJohn Newlands

Noticed when elements Noticed when elements were arranged by were arranged by atomic atomic massmass, they repeated , they repeated properties every properties every 88thth element.element.

He used the word He used the word periodicperiodic to describe this to describe this patternpattern

He gave it the name the He gave it the name the LawLaw of of OctavesOctaves

1838-1898

Unfortunately…Unfortunately…

Did notDid not work for all the elements work for all the elements Criticized because of its association with Criticized because of its association with

musicmusic Did give others the idea of repeating Did give others the idea of repeating

properties - properties - periodicperiodicWe Hate It

Lothar Lothar MeyerMeyer and Dmitri and Dmitri MendeleevMendeleev

Each made a connection between Each made a connection between atomic massatomic mass and and propertiesproperties of of elementselements

1830-1895 1834 - 1907

The winner is…The winner is…

Mendeleev is given credit because Mendeleev is given credit because his was his was publishedpublished first first

In addition, Mendeleev predicted In addition, Mendeleev predicted unknownunknown elements elements

However, not completely correct – However, not completely correct – newnew elements weren’t in elements weren’t in correctcorrect orderorder

What do you notice about elements What do you notice about elements 27 & 28 and 52 & 53?27 & 28 and 52 & 53?

MendeleevMendeleev

Henry MoseleyHenry Moseley

Solved this problem by Solved this problem by arranging the elements arranging the elements by increasing by increasing atomic atomic number.number.

The The periodicperiodic repetition repetition of chemical and of chemical and physical properties of physical properties of elements when elements when arranged by atomic arranged by atomic numbernumber is now known is now known as as PeriodicPeriodic Law Law

1887-1915

Which leads to the Modern Periodic Which leads to the Modern Periodic TableTable

Boxes each with:Boxes each with:

H1

Hydrogen

1.00794

Element Name

Atomic Number

Atomic Symbol

Atomic Mass

That are arranged by increasing atomic numbers

RememberRemember

Atomic number = the number of Atomic number = the number of protonsprotons = the number of = the number of electronselectrons (if (if neutral) neutral)

Atomic Mass on the Periodic table is Atomic Mass on the Periodic table is the average mass of the the average mass of the isotopesisotopes• But the mass number of each isotope is But the mass number of each isotope is

the the protonsprotons plus the plus the neutronsneutrons

Chemical SymbolChemical Symbol

The symbol that refers to the The symbol that refers to the elementelement First letter is First letter is capitalizedcapitalized, second letter (if , second letter (if

applicable) is applicable) is lowerlower case case Not all symbols are based on English Not all symbols are based on English

names for the elements, some come from names for the elements, some come from their Latin names or even other languagestheir Latin names or even other languages

– Silver – Ag – argentum– Antimony – Sb -stibium – Lead – Pb – plumbum – Copper – Cu – cyprium

– Tin – Sn – stannum– Iron – Fe - ferrum– Mercury – Hg - hydrargyrum– Gold – Au - aurum

Columns and RowsColumns and Rows

The columns are called The columns are called FamiliesFamilies or or GroupsGroups• Earlier Version had 1-8 followed by A or BEarlier Version had 1-8 followed by A or B

Group A elements are called Group A elements are called RepresentativeRepresentative Elements Elements Group B elements are called Group B elements are called TransitionTransition Elements Elements

• Modern Version labels the columns with 1-18Modern Version labels the columns with 1-18

Rows are called Rows are called PeriodsPeriods• Seven Seven periodsperiods for the seven for the seven energy levelsenergy levels (rings) (rings)

Classifying ElementsClassifying Elements

Three Types of ElementsThree Types of Elements• MetalsMetals• NonmetalsNonmetals• MetalloidsMetalloids

MetalsMetals

ShinyShiny when smooth and clean when smooth and clean SolidSolid at room temperature at room temperature

• Only exception - Only exception - MercuryMercury GoodGood conductors of heat and conductors of heat and

electricityelectricity

Most of the elements on the table are metals

NonmetalsNonmetals

Upper RightUpper Right side of the Periodic side of the Periodic TableTable

Generally Generally brittlebrittle solids or solids or gasesgases PoorPoor conductors of heat and conductors of heat and

electricityelectricity BromineBromine is the only liquid at room is the only liquid at room

temperaturetemperature

“The Yellow Elements”

MetalloidsMetalloids

A.k.a – the A.k.a – the semi-metalssemi-metals Boxes bordering the Boxes bordering the stair-stepstair-step Physical and chemical characteristics Physical and chemical characteristics

of of bothboth metals and nonmetals metals and nonmetals

“The Green Stair-stepping Elements”