u5: the history and arrangement of the periodic table

U5: The History U5: The History and Arrangement and Arrangement

of the Periodic of the Periodic TableTable

http://www.meta-synthesis.com/webbook/35_pt/pt.html

I. History of the Periodic TableI. History of the Periodic Table

►1869 – Dmitri Mendeleev (Russian Chemist) thought elements may have something in common.

►Made each element a card and listed its properties known at the time (mass, density, color, melting point and valence number).

►Organized the elements into a table according to their atomic mass.

Dmitri Mendeleev – Dmitri Mendeleev – Columns = Groups/FamiliesColumns = Groups/Families

►Noticed a repeating pattern of valence electrons (1,2,3,4,5 etc..)

►Noticed elements fell in to columns (groups or families)

►Noticed all elements in a column had the same valence electrons and showed similar physical and chemical properties.

Amazing Facts with his cards!Amazing Facts with his cards!

►Mendeleev left blank spaces in his table so elements would line up – he also predicted what properties the undiscovered elements would have.

►He predicted properties of five of these elements and their compounds. Three of these missing elements were discovered by others within 15 years.

►The element, atomic number 101, has been named after Mendeleev.

Mendeleev’s Periodic Table by atomic mass (with empty spaces for elements that would soon be

discovered)

Henry MoseleyHenry Moseley

►1913 – Henry Moseley (English Scientist) changed the arrangement of the periodic table.

►Instead of by increasing atomic mass , Moseley arranged the elements by increasing: atomic number (# of protons).

Interesting fact: Moseley's law = the energy of x-rays emitted from an element is related to its atomic number.

II. Arrangement of the Periodic II. Arrangement of the Periodic TableTable

►Systematic arrangement of the elements by atomic number and chemical properties

►Divided into Regions: Metals, Nonmetals and Metalloids

►Vertical Columns – Numbered groups/families

►Horizontal Rows - Periods are by amount of energy levels (1-7) or orbital shells

III. REGIONS

Metals - location, Metals - location, propertiesproperties

►Elements on the Elements on the leftleft side of the side of the table table

►Good conductors Good conductors of electricityof electricity►ShinyShiny►DuctileDuctile – can be drawn into thin – can be drawn into thin

wireswires►MalleableMalleable – can be hammered into – can be hammered into

thin sheets or shapesthin sheets or shapes►High melting pointHigh melting point►Tend to lose electronsTend to lose electrons

Nonmetals - location, Nonmetals - location, propertiesproperties

► Elements on the Elements on the rightright of the of the zigzag zigzag on on the tablethe table

►Do not conduct electricity Do not conduct electricity or heator heat►DullDull in appearance, not shiny in appearance, not shiny►Brittle Brittle or break easilyor break easily►Not DuctileNot Ductile or Malleable (cannot be or Malleable (cannot be

drawn into wire or hammered into drawn into wire or hammered into sheets)sheets)

► Lower densitiesLower densities► Lower melting points Lower melting points ► Tend to gain electrons or share electrons Tend to gain electrons or share electrons

with each otherwith each other

Metalloids - location, Metalloids - location, properties properties

► Elements that are found along Elements that are found along bothboth sides of the zigzag line (except for Al)sides of the zigzag line (except for Al)

► Properties of both metals and Properties of both metals and nonmetalsnonmetals

► SemiconductorsSemiconductors - conduct heat and - conduct heat and electricity better than nonmetals but electricity better than nonmetals but not as well as metalsnot as well as metals

► SolidsSolids► Can be Can be shinyshiny or or dulldull►Both ductile and malleableBoth ductile and malleable

IV. Chemical Groups IV. Chemical Groups (Families)(Families)

►Elements that are in the same group or family (column) of the Periodic Table have similar properties because they have the same number of valence electrons

►Very reactive , bonds easily with other substances (unstable and explosive)

►Never found alone in nature►Soft, silver-white, shiny

►1 valence electron in outer energy level

►Easily lose 1 electron to form a stable +1 ion

►Forms ionic bonds

Group (Family) 1 - Alkali Group (Family) 1 - Alkali MetalsMetals

Think it Over:►Hydrogen is a nonmetal gas, and

forms covalent bonds. So why is it in the Alkali Metal family?

Group/Family 2 - Alkaline Earth Group/Family 2 - Alkaline Earth MetalsMetals

►2nd most reactive elements, bond easily with other substances, unstable

►Never found alone in nature

►2 valence electrons in outer energy level

►Loses 2 electrons to form stable +2 ions

►Forms ionic bonds

Groups 3-12 The Transition Groups 3-12 The Transition Metals Metals

►Unpredictable►Common metals – gold, silver & copper

►Can lose and/or share valence electrons

►Forms Metallic Bonds

Rare Earth ElementsRare Earth Elements(Inner Transition Metals)(Inner Transition Metals)

►First Row – Lanthanide Series

- naturally found rare Earth metals

- all but one is non-radioactive

►Second Row – Actinide Series

- most are man-made and

most are radioactive - many are short-lived

From Metals to NonmetalsFrom Metals to Nonmetals

Group Group ##

NameName Valence Valence ElectronElectronss

BondsBonds RegionRegion

1313 Boron Boron FamilyFamily

33 CovalenCovalentt

IonicIonic

(lose)(lose)

MetalloidMetalloids & s & MetalsMetals

1414 Carbon Carbon FamilyFamily

Basis of Basis of LifeLife

44 CovalenCovalentt

Metals, Metals, MetalloidMetalloids s NonmetaNonmetalsls


Group Group ##

NameName Valence Valence ElectroElectronsns


1515 NitrogeNitrogenn

55 CovalentCovalent

Ionic (Gains)Ionic (Gains)Metals, Metals, MetalloidMetalloids s NonmetalNonmetalss

1616 OxygenOxygen 66 Covalent orCovalent or

Ionic (Gains Ionic (Gains

electrons)electrons)

Metals, Metals, MetalloidMetalloids s NonmetalNonmetalss


* Helium has a full outer shell * Helium has a full outer shell with 2 valence electronswith 2 valence electrons

Group Group ##

NameName Valence Valence ElectronElectronss


1717 HalogenHalogen 77 Covalent orCovalent or

Ionic Ionic

(Gains (Gains Electrons)Electrons)

NonmetaNonmetalsls

VeryVery

ReactiveReactive

1818 Noble Noble Gases Gases or Inert or Inert GasesGases

8*8* Does not bondDoes not bond

StableStable

Non reactiveNon reactive

Full outer shellsFull outer shells

NonmetaNonmetalsls

Stability

• Groups 1-17 are unstable ►The Noble Gas group/family is

stable

►Think it Over: What makes an element stable?

Point to Ponder►The element Carbon is the “Basis of

Life”. What is meant by this?

u5: the history and arrangement of the periodic table

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