chapter 5 atomic structure & periodic table. atomic structure democritus teacher, 4 th century...

CHAPTER 5CHAPTER 5

ATOMIC STRUCTUREATOMIC STRUCTURE

& PERIODIC TABLE& PERIODIC TABLE

ATOMIC STRUCTUREATOMIC STRUCTURE

DEMOCRITUSDEMOCRITUSTEACHER, 4TEACHER, 4thth Century BC Century BC

ATOMIST SCHOOL of ATOMIST SCHOOL of THOUGHTTHOUGHT

ATOMIC STRUCTUREATOMIC STRUCTURE

MATTERMATTER TINY PARTCLES CALLED ATOMSTINY PARTCLES CALLED ATOMS

ATOMSATOMSFUNDAMENTAL UNITS OF MATTERFUNDAMENTAL UNITS OF MATTER

INVISIBLEINVISIBLE

INDESTRUCTABLEINDESTRUCTABLE

ATOMIC STRUCTUREATOMIC STRUCTURE

JOHN DALTONJOHN DALTON (1766-1844) (1766-1844) ENGLISH SCHOOL TEACHERENGLISH SCHOOL TEACHER

STUDIED ELEMENTAL RATIOS STUDIED ELEMENTAL RATIOS IN CHEMICAL REACTIONSIN CHEMICAL REACTIONS

DALTON’S ATOMIC THEORYDALTON’S ATOMIC THEORY

ATOMIC STRUCTUREATOMIC STRUCTURE

DALTON’S ATOMIC THEORYDALTON’S ATOMIC THEORYELEMENTS ARE COMPOSED OF ELEMENTS ARE COMPOSED OF

SUBMICROSCOPIC INDIVISIBLE SUBMICROSCOPIC INDIVISIBLE PARTICLES – ATOMSPARTICLES – ATOMS

ATOMS OF THE SAME ELEMENT ARE ATOMS OF THE SAME ELEMENT ARE IDENTICAL IDENTICAL

ATOMS OF ANY 1 ELEMENT ARE DIFFERENT ATOMS OF ANY 1 ELEMENT ARE DIFFERENT FROM ATOMS OF ANY OTHER ELEMENTFROM ATOMS OF ANY OTHER ELEMENT

ATOMIC STRUCTUREATOMIC STRUCTURE

DALTON’S ATOMIC THEORYDALTON’S ATOMIC THEORYATOMS OF DIFFERENT ELEMENTS CAN MIX ATOMS OF DIFFERENT ELEMENTS CAN MIX

TOGETHER or CHEMICALLY COMBINE TO TOGETHER or CHEMICALLY COMBINE TO FORM COMPOUNDS IN SIMPLE WHOLE FORM COMPOUNDS IN SIMPLE WHOLE NUMBER RATIOSNUMBER RATIOS

CHEMICAL REACTIONS OCCUR WHEN CHEMICAL REACTIONS OCCUR WHEN ATOMS ARE SEPARATED, JOINED OR ATOMS ARE SEPARATED, JOINED OR REARRANGEDREARRANGED

ATOMIC STRUCTUREATOMIC STRUCTURE

DALTON’S ATOMIC THEORYDALTON’S ATOMIC THEORYATOMS OF ONE ELEMENT ARE NEVER ATOMS OF ONE ELEMENT ARE NEVER

CHANGED INTO ATOMS OF ANTOHER CHANGED INTO ATOMS OF ANTOHER ELEMENT AS A RESULT OF A CHEMICAL ELEMENT AS A RESULT OF A CHEMICAL REACTIONREACTION

TODAY, MUCH OF THEORY STILL VALID TODAY, MUCH OF THEORY STILL VALID EXCEPT THAT ATOMS ARE NOT EXCEPT THAT ATOMS ARE NOT INDIVISIBLEINDIVISIBLE

THE ATOMTHE ATOM

SMALLEST PARTICLE OF AN SMALLEST PARTICLE OF AN ELEMENT THAT RETAINS THE ELEMENT THAT RETAINS THE ELEMENT’S PROPERTIESELEMENT’S PROPERTIES

THE ATOM’S SIZETHE ATOM’S SIZEIF YOU PLACED 100,000,000 COPPER IF YOU PLACED 100,000,000 COPPER

ATOMS SIDE BY SIDE, THE LINE ATOMS SIDE BY SIDE, THE LINE WOULD BE 1 cm LONGWOULD BE 1 cm LONG

J. J. THOMSONJ. J. THOMSON

ENGLISH PHYSICISTENGLISH PHYSICIST1897 – DISCOVERED ELECTRONS 1897 – DISCOVERED ELECTRONS

NEGATIVELY CHARGENEGATIVELY CHARGE

SUBATOMIC PARTICLESSUBATOMIC PARTICLES

EXPERIMENTS USED FLOW OF EXPERIMENTS USED FLOW OF ELECTRIC CURRENT THROUGH ELECTRIC CURRENT THROUGH GASESGASES

CATHODE RAY TUBECATHODE RAY TUBE

CATHODE RAY TUBECATHODE RAY TUBE

CATHODE RAYS WERE ATTRACTED TO CATHODE RAYS WERE ATTRACTED TO POSITIVELY CHARGED METAL PLATESPOSITIVELY CHARGED METAL PLATES

NEGATIVELY CHARGED PLATES REPELLED NEGATIVELY CHARGED PLATES REPELLED THE RAYTHE RAY

IF LIKE CHARGES REPEL AND OPPOSITE IF LIKE CHARGES REPEL AND OPPOSITE CHARGES ATTRACT, RAY IS MADE UP OF CHARGES ATTRACT, RAY IS MADE UP OF NEGATIVE CHARGED PARTICLES, i.e. NEGATIVE CHARGED PARTICLES, i.e. ELECTRONSELECTRONS

DEFLECTION of CATHODE RAYDEFLECTION of CATHODE RAY

CATHODE RAY CATHODE RAY

CATHODE RAY PRODUCTION WAS CATHODE RAY PRODUCTION WAS INDEPENDENT OF TYPE OF GASINDEPENDENT OF TYPE OF GAS

ELECTRON PARTICLES WERE PART OF ELECTRON PARTICLES WERE PART OF EVERY ATOMEVERY ATOM

DETERMINED ELECTRON MASS WAS 1/2000 DETERMINED ELECTRON MASS WAS 1/2000 THE MASS OF A HYDROGEN ATOMTHE MASS OF A HYDROGEN ATOM

MATTER AND MATTER AND ELECTRIC CHARGEELECTRIC CHARGE

ATOMS HAVE NO NET CHARGEATOMS HAVE NO NET CHARGE

CHARGES ARE CARRIED BY PARTICLES OF CHARGES ARE CARRIED BY PARTICLES OF MATTERMATTER

CHARGES ALWAYS EXIST IN WHOLE CHARGES ALWAYS EXIST IN WHOLE NUMBER MULTIPLES OF A SINGLE BASIC NUMBER MULTIPLES OF A SINGLE BASIC UNITUNIT

WHEN AN EQUAL NUMBER OF NEGATIVE WHEN AN EQUAL NUMBER OF NEGATIVE CHARGES COMBINE WITH AN EQUAL CHARGES COMBINE WITH AN EQUAL NUMBER OF POSITIVE CHARGES, THE NUMBER OF POSITIVE CHARGES, THE PARTICLE HAS NO NET CHARGEPARTICLE HAS NO NET CHARGE

PROTONSPROTONS

A POSITIVELY CHARGED PARTICLE MUST A POSITIVELY CHARGED PARTICLE MUST BE PRESENT TO BALANCE EACH BE PRESENT TO BALANCE EACH NEGATIVELY CHARGED ELECTRONNEGATIVELY CHARGED ELECTRON

EVIDENCE OF THESE PARTICLES WERE EVIDENCE OF THESE PARTICLES WERE PRESENTED BY E. GOLDSTEIN IN 1886PRESENTED BY E. GOLDSTEIN IN 1886– OBSERVED A RAY TRAVELING IN THE OBSERVED A RAY TRAVELING IN THE

OPPOSITE DIRECTION OF THE CATHODE RAY OPPOSITE DIRECTION OF THE CATHODE RAY – CANAL RAY– CANAL RAY

– CANAL RAY MADE UP OF POSITIVE CANAL RAY MADE UP OF POSITIVE PARTICLES - PROTONSPARTICLES - PROTONS

THE NEUTRONTHE NEUTRON

IN 1932, JAMES CHADWICK (English IN 1932, JAMES CHADWICK (English physicist 1891-1974) CONFIRMED THE physicist 1891-1974) CONFIRMED THE EXISTENCE OF ANOTHER SUB-ATOMIC EXISTENCE OF ANOTHER SUB-ATOMIC PARTICLE – PARTICLE – NEUTRONNEUTRON

NEUTRONS HAVE MASS SIMILAR TO NEUTRONS HAVE MASS SIMILAR TO PROTONS, BUT NO CHARGEPROTONS, BUT NO CHARGE

THE ATOMIC NUCLEUSTHE ATOMIC NUCLEUS

BECAUSE OF SMALL SIZE, ATOM WAS BECAUSE OF SMALL SIZE, ATOM WAS DIFICULT TO STUDYDIFICULT TO STUDY

ORIGINALLY BELIEVED THAT ORIGINALLY BELIEVED THAT POSITIOVE AND NEGATIVE POSITIOVE AND NEGATIVE CHARGES WERE DISTRIBUTED CHARGES WERE DISTRIBUTED EVENLY THROUGHOUT ATOMEVENLY THROUGHOUT ATOM

THE ATOMIC NUCLEUSTHE ATOMIC NUCLEUS

ERNEST RUTHERFORDERNEST RUTHERFORD (1871-1937) (1871-1937)

University of Manchester, EnglandUniversity of Manchester, England

TESTED THEORY OF ATOMIC STRUCTURETESTED THEORY OF ATOMIC STRUCTURE

BOMBARDED GOLD FOIL WITH ALPHA BOMBARDED GOLD FOIL WITH ALPHA PARTICLE BEAMPARTICLE BEAM

IF POSITIVE CHARGE EVENLY SPREAD IN IF POSITIVE CHARGE EVENLY SPREAD IN ATOM, BEAM SHOULD PASS THROUGHATOM, BEAM SHOULD PASS THROUGH

RUTHERFORD’S EXPERIMENTRUTHERFORD’S EXPERIMENTRutherford and coworkers aimed a beam of alpha particles at a sheet of gold foil surrounded by a florescent screen.

RUTHERFORD’S EXPERIMENTRUTHERFORD’S EXPERIMENT

Most particles passed through with no deflection, while some were highly deflectedRutherford concluded that most particles passed through because the atom is mostly empty space.

RUTHERFORD’S RUTHERFORD’S EXPERIMENTEXPERIMENT

CONCLUDED THAT ALL OF POSITIVE CONCLUDED THAT ALL OF POSITIVE CHARGE AND MOST OF ATOM’S MASS CHARGE AND MOST OF ATOM’S MASS ARE CONCENTRATED IN A SMALL COREARE CONCENTRATED IN A SMALL CORE

THIS REGION WOULD HAVE A POSITIVE THIS REGION WOULD HAVE A POSITIVE CHARGE CAPABLE OF DEFLECTING CHARGE CAPABLE OF DEFLECTING BEAMBEAM

THIS REGION WAS CALLED THE THIS REGION WAS CALLED THE NUCLEUSNUCLEUS

DISTINGUISHING ATOMSDISTINGUISHING ATOMS

ATOMIC NUMBERATOMIC NUMBERUNIQUE FOR EACH ELEMENTUNIQUE FOR EACH ELEMENT

EQUALS THE NUMBER OF PROTONS IN EQUALS THE NUMBER OF PROTONS IN THE ELEMENT’S ATOMTHE ELEMENT’S ATOM

NUMBER OF PROTONS MUST EQUAL NUMBER OF PROTONS MUST EQUAL NUMBER OF ELECTRONS FOR NUMBER OF ELECTRONS FOR NEUTRAL ATOMNEUTRAL ATOM

DISTINGUISHING ATOMSDISTINGUISHING ATOMS

ATOMIC MASS NUMBERATOMIC MASS NUMBER

MASS IS CONCENTRATED IN THE MASS IS CONCENTRATED IN THE NUCLEUSNUCLEUS

DEPENDS ON THE NUMBER OF DEPENDS ON THE NUMBER OF PROTONS & NEUTRONSPROTONS & NEUTRONS

ElementElement SymboSymboll

Atomic Atomic ##

Mass Mass ##

# of # of NeutronsNeutrons

Nitrogen-Nitrogen-1515

Neon-22Neon-22

BerylliumBeryllium-9-9

DISTINGUISHING ATOMSDISTINGUISHING ATOMS

DISTINGUISHING ATOMSDISTINGUISHING ATOMS

ISOTOPESEQUAL NUMBER OF PROTONS &

ELECTRONS

DIFFERENT NUMBER OF NEUTRONS

DIFFERENT MASS NUMBER

CHEMICALLY ALIKE

DISTINGUISHING ATOMSDISTINGUISHING ATOMS

Atomic MassAtomic MassMass of proton or neutron is small Mass of proton or neutron is small

(1.67 x 10(1.67 x 10-24 -24 g)g)

Mass of electron is negligible in Mass of electron is negligible in comparison (9.11 x 10comparison (9.11 x 10-28 -28 g)g)

The mass of even the largest atom is The mass of even the largest atom is incredibly smallincredibly small

DISTINGUISHING ATOMSDISTINGUISHING ATOMS

Compare relative mass using a Compare relative mass using a reference isotope as a standardreference isotope as a standard

Isotope C-12 assigned a mass of 12 Isotope C-12 assigned a mass of 12 amuamu

Atomic mass unit (amu) defined as Atomic mass unit (amu) defined as one-twelfth the mass of carbon-12one-twelfth the mass of carbon-12

DISTINGUISHING ATOMSDISTINGUISHING ATOMS

If atomic mass is determined by the If atomic mass is determined by the number of protons and electrons, why number of protons and electrons, why isn’t the mass of an element a whole isn’t the mass of an element a whole number?number?

Most elements occur as a mixture of two Most elements occur as a mixture of two or more isotopes.or more isotopes.

DISTINGUISHING ATOMSDISTINGUISHING ATOMS

The atomic mass of an element is a The atomic mass of an element is a weighted average mass of the weighted average mass of the atoms in a naturally occurring atoms in a naturally occurring sample of the element.sample of the element.

DISTINGUISHING ATOMSDISTINGUISHING ATOMS

You can calculate the atomic mass if You can calculate the atomic mass if you know three values:you know three values:

The number of stable isotopes of The number of stable isotopes of the element.the element.

The mass of each isotope.The mass of each isotope.

The natural percent abundance of The natural percent abundance of each isotope.each isotope.

MASS DEFECTMASS DEFECT

Calculate the mass defect of a chlorine-35 Calculate the mass defect of a chlorine-35 atom. atom.

The actual mass of chlorine-35 is 5.81 x The actual mass of chlorine-35 is 5.81 x 1010-23 -23 gramsgrams

e = 9.11 x 10e = 9.11 x 10-28 -28 gg

p = 1.67 x 10p = 1.67 x 10-24 -24 gg

n = 1.67 x 10n = 1.67 x 10-24 -24 gg

THE PERIODIC TABLETHE PERIODIC TABLE

Dmitri Mendeleev (1834-1907)Dmitri Mendeleev (1834-1907)

Russian chemistRussian chemist

Listed elements in columns in order of Listed elements in columns in order of increasing atomic mass.increasing atomic mass.

Arranged columns so that elements Arranged columns so that elements with similar properties were side by with similar properties were side by side.side.

THE PERIODIC TABLETHE PERIODIC TABLE

Medeleev left blank spaces Medeleev left blank spaces where there were no known where there were no known elements with the appropriate elements with the appropriate properties or mass.properties or mass.

Predicted the properties of the Predicted the properties of the missing elements.missing elements.

THE PERIODIC TABLETHE PERIODIC TABLE

Henry Mosely (1887-1915)Henry Mosely (1887-1915)British PhysicistBritish Physicist

Determined the atomic number of the Determined the atomic number of the atoms of the elements.atoms of the elements.

Arranged elements in table by atomic Arranged elements in table by atomic number instead of mass.number instead of mass.

THE MODERN THE MODERN PERIODIC TABLEPERIODIC TABLE

Each horizontal row is a periodEach horizontal row is a periodSeven periodsSeven periodsFrom 2 to 32 elements in a periodFrom 2 to 32 elements in a periodProperties of the elements change as Properties of the elements change as

you move across a period.you move across a period.This pattern repeats from period to This pattern repeats from period to

periodperiod

The Periodic LawThe Periodic Law

THE MODERN THE MODERN PERIODIC TABLEPERIODIC TABLE

Each column is a group or familyEach column is a group or familyElements in a group have similar Elements in a group have similar

physical and chemical propertiesphysical and chemical propertiesGroups are identified by a number and Groups are identified by a number and

the letter A or Bthe letter A or BGroup A are the representative elementsGroup A are the representative elementsGroup A can be divided into three broad Group A can be divided into three broad

classesclasses

THE MODERN THE MODERN PERIODIC TABLEPERIODIC TABLE

METALSMETALSHIGH ELECTRICAL CONDUCTIVITYHIGH ELECTRICAL CONDUCTIVITY

HIGH LUSTERHIGH LUSTER

DUCTILEDUCTILE

MALLEABLEMALLEABLE

THE MODERN THE MODERN PERIODIC TABLEPERIODIC TABLE

METALSMETALSALKALI METALS ALKALI METALS

ALKALINE EARTH METALSALKALINE EARTH METALS

TRANSITION METALSTRANSITION METALS

INNER TRANSITION METALSINNER TRANSITION METALS

THE MODERN THE MODERN PERIODIC TABLEPERIODIC TABLE

NON-METALSNON-METALSPOOR ELECTRICAL CONDUCTIVITYPOOR ELECTRICAL CONDUCTIVITY

NON-LUSTRIOUSNON-LUSTRIOUS

THE MODERN THE MODERN PERIODIC TABLEPERIODIC TABLE

NON-METALSNON-METALSHALOGENSHALOGENS

NOBLE GASESNOBLE GASES

THE MODERN THE MODERN PERIODIC TABLEPERIODIC TABLE

METALLOIDSMETALLOIDS

Elements with properties that Elements with properties that are intermediate between are intermediate between

those those of metals and non-metals.of metals and non-metals.