Embed Size (px)
Citation preview
Chapter 2:Chemical Foundations
The Early History of Chemistry
Fundamental Chemical Laws
Dalton’s Atomic Theory
Early Characterizations of Atoms
The Modern View of Atomic Structure
Molecules and Ions
Introduction to the Periodic Table
Naming Simple Compounds
HistoryHistoryGreeksGreeks (400 BC):(400 BC): first to explain why chemical first to explain why chemical
changes occur.changes occur.Democritus and LeucippusDemocritus and Leucippus - - atomosatomosAristotleAristotle - elements.- elements.
AlchemyAlchemyRobert BoyleRobert Boyle (1660): experimental definition of (1660): experimental definition of
element & perform truly quantitative experiments.element & perform truly quantitative experiments.
A. LavoisierA. Lavoisier (1789):(1789): Father of modern chemistry.Father of modern chemistry.He wrote the first modern chemistry book.He wrote the first modern chemistry book.
LawsLaws• Conservation of MassConservation of Mass
Antoine LavoisierAntoine Lavoisier finally finally explained the true nature explained the true nature
of combustion.of combustion.
LawsLaws• Law of Definite ProportionLaw of Definite Proportion
Joseph Proust:Joseph Proust: compounds have compounds have a constant composition.a constant composition.
They react in specific ratios by They react in specific ratios by mass.mass.
LawsLaws• Multiple Proportions -Multiple Proportions -
When two elements form When two elements form more than one compound, more than one compound, the ratios of the masses of the ratios of the masses of the second element that the second element that combine with one gram of combine with one gram of the first can be reduced to the first can be reduced to small whole numbers.small whole numbers.
John DaltonJohn Dalton
What?!What?!• Water has 8 grams of oxygen per gram Water has 8 grams of oxygen per gram
of hydrogen.of hydrogen.
• Hydrogen peroxide has 16 grams of Hydrogen peroxide has 16 grams of oxygen per gram of hydrogen.oxygen per gram of hydrogen.
• 16/8 = 2/116/8 = 2/1
• Small whole number ratios.Small whole number ratios.
Dalton’s Atomic TheoryDalton’s Atomic Theory
1)1) Elements are made up Elements are made up of atoms.of atoms.
2)2) Atoms of each element Atoms of each element are identical. Atoms of are identical. Atoms of different elements are different elements are different.different.
Dalton’s Atomic TheoryDalton’s Atomic Theory3)3) Compounds are formed Compounds are formed
when atoms combine. when atoms combine. Each compound has a Each compound has a specific number and specific number and kinds of atom.kinds of atom.
4)4) Chemical reactions are Chemical reactions are rearrangement of rearrangement of atoms. Atoms are not atoms. Atoms are not created or destroyed.created or destroyed.
• Gay-Lussac -Gay-Lussac - under the same conditions of under the same conditions of temperature and pressure, compounds temperature and pressure, compounds always react in whole number ratios by always react in whole number ratios by volume.volume.
• Avagadro -Avagadro - interpreted that to mean at the interpreted that to mean at the same temperature and pressure, equal same temperature and pressure, equal volumes of gas contain the same number of volumes of gas contain the same number of particles (called particles (called Avagadro’s HypothesisAvagadro’s Hypothesis).).
Additional ObservationsAdditional Observations
The ElectronThe Electron• Streams of negatively charged particles were Streams of negatively charged particles were
found to emanate from cathode tubes.found to emanate from cathode tubes.
• J. J. Thompson is credited with their discovery J. J. Thompson is credited with their discovery (1897).(1897).
The ElectronThe Electron• Thompson measured the charge/mass ratio of the Thompson measured the charge/mass ratio of the
electron to be 1.76 electron to be 1.76 10 1088 coulombs/g. coulombs/g.
Millikan Oil Drop ExperimentMillikan Oil Drop Experiment
Once the charge/mass Once the charge/mass ratio of the electron ratio of the electron was known, was known, determination of determination of either the charge or either the charge or the mass of an the mass of an electron would yield electron would yield the other.the other.
Millikan Oil Drop ExperimentMillikan Oil Drop Experiment
Robert Millikan Robert Millikan (University of (University of Chicago) determined Chicago) determined the charge on the the charge on the electron in 1909.electron in 1909.
The Atom, circa 1900The Atom, circa 1900
• ““Plum pudding” Plum pudding” model, put forward model, put forward by Thompson.by Thompson.
• Positive sphere of Positive sphere of matter with negative matter with negative electrons imbedded electrons imbedded in it.in it.
Discovery of the NucleusDiscovery of the Nucleus
Ernest Rutherford Ernest Rutherford shot shot particles at a particles at a thin sheet of gold thin sheet of gold foil and observed foil and observed the pattern of the pattern of scatter of the scatter of the particles.particles.
The Nuclear AtomThe Nuclear Atom
Since some particles Since some particles were deflected at were deflected at large angles, large angles, Thompson’s model Thompson’s model could not be correct.could not be correct.
The Nuclear AtomThe Nuclear Atom
• Rutherford postulated a very small, dense Rutherford postulated a very small, dense nucleus with the electrons around the nucleus with the electrons around the outside of the atom.outside of the atom.
• Most of the volume of the atom is empty Most of the volume of the atom is empty space.space.
RadioactivityRadioactivity
• The spontaneous emission of radiation The spontaneous emission of radiation by an atom.by an atom.
• First observed by Henri Becquerel.First observed by Henri Becquerel.
• Also studied by Marie and Pierre Also studied by Marie and Pierre Curie.Curie.
RadioactivityRadioactivity• Three types of radiation were discovered by Three types of radiation were discovered by
Ernest Rutherford:Ernest Rutherford: particlesparticles particlesparticles raysrays
Other Subatomic ParticlesOther Subatomic Particles
• Protons were discovered by Rutherford Protons were discovered by Rutherford in 1919.in 1919.
• Neutrons were discovered by James Neutrons were discovered by James Chadwick in 1932.Chadwick in 1932.
Subatomic ParticlesSubatomic Particles
• Protons and electrons are the only particles that have Protons and electrons are the only particles that have a charge.a charge.
• Protons and neutrons have essentially the same mass.Protons and neutrons have essentially the same mass.
• The mass of an electron is so small we ignore it.The mass of an electron is so small we ignore it.
Symbols of ElementsSymbols of Elements
Elements are symbolized by one or two Elements are symbolized by one or two letters.letters.
Atomic NumberAtomic Number
All atoms of the same element have the All atoms of the same element have the same number of protons: same number of protons:
The atomic number (Z)The atomic number (Z)
Atomic MassAtomic Mass
The The mass number (A)mass number (A) of an atom in atomic of an atom in atomic mass units mass units (amu)(amu) is the total number of is the total number of protons and neutrons in the atom.protons and neutrons in the atom.
Isotopes:Isotopes:
• Atoms of the same element with different masses.Atoms of the same element with different masses.
• Isotopes have different numbers of neutrons.Isotopes have different numbers of neutrons.
116C
126C
136C
146C
Atomic MassAtomic Mass
Atomic and molecular masses can be measured Atomic and molecular masses can be measured with great accuracy with a mass spectrometer.with great accuracy with a mass spectrometer.
Average MassAverage Mass
• Because in the real world we use large Because in the real world we use large amounts of atoms and molecules, we amounts of atoms and molecules, we use average masses in calculations.use average masses in calculations.
• Average mass is calculated from the Average mass is calculated from the isotopes of an element weighted by isotopes of an element weighted by their relative abundances.their relative abundances.
Periodic Table:Periodic Table:
• A systematic A systematic catalog of catalog of elements.elements.
• Elements are Elements are arranged in order arranged in order of atomic of atomic number.number.
PeriodicityPeriodicity
When one looks at the chemical properties When one looks at the chemical properties of elements, one notices a repeating pattern of elements, one notices a repeating pattern of reactivities.of reactivities.
Periodic TablePeriodic Table
• The rows on the The rows on the periodic chart are periodic chart are periods.periods.
• Columns are groups.Columns are groups.
• Elements in the sameElements in the same group have similar group have similar chemical properties.chemical properties.
GroupsGroups
These five groups are known by their These five groups are known by their names.names.
Periodic TablePeriodic Table
Nonmetals are on Nonmetals are on the right side of the the right side of the periodic table (with periodic table (with the exception of H).the exception of H).
Periodic TablePeriodic Table
Metalloids border Metalloids border the stair-step line the stair-step line (with the exception (with the exception of Al and Po).of Al and Po).
Periodic TablePeriodic Table
Metals are on the Metals are on the left side of the left side of the chart.chart.
Chemical FormulasChemical Formulas
The subscript to the The subscript to the right of the symbol of an right of the symbol of an element tells the number element tells the number of atoms of that element of atoms of that element in one molecule of the in one molecule of the compound.compound.
Diatomic MoleculesDiatomic Molecules
These seven elements occur naturally as These seven elements occur naturally as molecules containing two atoms.molecules containing two atoms.
Types of FormulasTypes of Formulas
• Empirical formulasEmpirical formulas give the lowest give the lowest whole-number ratio of atoms of each whole-number ratio of atoms of each element in a compound.element in a compound.
• Molecular formulasMolecular formulas give the exact give the exact number of atoms of each element in a number of atoms of each element in a compound.compound.
Types of FormulasTypes of Formulas
• Structural formulasStructural formulas show the show the order in which atoms are order in which atoms are bonded.bonded.
• Perspective drawingsPerspective drawings also show also show the three-dimensional array of the three-dimensional array of atoms in a compound.atoms in a compound.
• Ball-and-stick modelBall-and-stick model• Space-filling modelSpace-filling model
IonsIons
• When atoms lose or gain electrons, they When atoms lose or gain electrons, they become ions.become ions.Cations are positive and are formed by Cations are positive and are formed by
elements on the left side of the periodic chart.elements on the left side of the periodic chart.Anions are negative and are formed by Anions are negative and are formed by
elements on the right side of the periodic chart.elements on the right side of the periodic chart.
Ionic BondsIonic Bonds
Ionic compounds (such as NaCl) are generally Ionic compounds (such as NaCl) are generally formed between metals and nonmetals.formed between metals and nonmetals.
Writing FormulasWriting Formulas
• Because compounds are electrically neutral, Because compounds are electrically neutral, one can determine the formula of a one can determine the formula of a compound this way:compound this way:The charge on the cation becomes the subscript The charge on the cation becomes the subscript
on the anion.on the anion.The charge on the anion becomes the subscript The charge on the anion becomes the subscript
on the cation.on the cation.If these subscripts are not in the lowest whole-If these subscripts are not in the lowest whole-
number ratio, divide them by the greatest number ratio, divide them by the greatest common factor.common factor.
Inorganic NomenclatureInorganic Nomenclature
• Write the name of the cation.Write the name of the cation.• If the anion is an element, change its If the anion is an element, change its
ending to -ending to -ideide; if the anion is a ; if the anion is a polyatomic ion, simply write the name polyatomic ion, simply write the name of the polyatomic ion.of the polyatomic ion.
• If the cation can have more than one If the cation can have more than one possible charge, write the charge as a possible charge, write the charge as a Roman numeral in parentheses.Roman numeral in parentheses.
• The less electronegative The less electronegative atom is usually listed first.atom is usually listed first.
• A prefix is used to denote A prefix is used to denote the number of atoms of the number of atoms of each element in the each element in the compound (compound (monomono- - is not is not used on the first element used on the first element listed, however.)listed, however.)
Nomenclature of BinaryNomenclature of BinaryCompoundsCompounds
• The ending on the more The ending on the more electronegative element is electronegative element is changed to changed to --ide.ide.
COCO22: carbon dioxide: carbon dioxideCClCCl44: carbon tetrachloride: carbon tetrachloride
Nomenclature of BinaryNomenclature of BinaryCompoundsCompounds
Nomenclature of BinaryNomenclature of BinaryCompoundsCompounds
If the prefix ends with If the prefix ends with aa or or oo and the name of the and the name of the element begins with a element begins with a vowel, the two vowel, the two successive vowels are successive vowels are often turned into one:often turned into one:
NN22OO55::
dinitrogendinitrogen pentoxidepentoxide
• When there are two oxyanions When there are two oxyanions involving the same element:involving the same element:The one with fewer oxygens ends in -The one with fewer oxygens ends in -iteite
• NONO22− − : nitrite: nitrite; ; SOSO33
22− − : sulfite: sulfite
The one with more oxygens ends in -The one with more oxygens ends in -ateate• NONO33
− − : nitrate; SO: nitrate; SO4422− − : sulfate: sulfate
Patterns in Oxyanion Patterns in Oxyanion NomenclatureNomenclature
Patterns in Oxyanion Patterns in Oxyanion NomenclatureNomenclature
• The one with the second fewest oxygens ends in -ite
ClO2− : chlorite
• The one with the second most oxygens ends in -ate
ClO3− : chlorate
• The one with the fewest oxygens has the The one with the fewest oxygens has the prefix prefix hypohypo-- and ends in - and ends in -iteite
ClOClO−− : hypochlorite: hypochlorite
• The one with the most oxygens has the The one with the most oxygens has the prefix prefix perper-- and ends in - and ends in -ateate
ClOClO44−− : perchlorate: perchlorate
Patterns in Oxyanion Patterns in Oxyanion NomenclatureNomenclature
Acid NomenclatureAcid Nomenclature
• If the anion in the acid If the anion in the acid ends in ends in --ideide, change , change the ending to the ending to --icic acid acid and add the prefix and add the prefix hydrohydro-- ::HCl: hydrochloric HCl: hydrochloric
acidacidHBr: hydrobromic HBr: hydrobromic
acidacidHI: hydroiodic acidHI: hydroiodic acid
Acid NomenclatureAcid Nomenclature
• If the anion in the If the anion in the acid ends in acid ends in --iteite, , change the ending to change the ending to --ousous acid acid::HClO: hypochlorous HClO: hypochlorous
acidacidHClOHClO22: chlorous acid: chlorous acid
Acid NomenclatureAcid Nomenclature
• If the anion in the If the anion in the acid ends in acid ends in --ateate, , change the ending to change the ending to --icic acid:acid:HClOHClO33: chloric acid: chloric acid
HClOHClO44: perchloric : perchloric
acidacid
Chapter 2:Chemical Foundations
The Early History of Chemistry
Fundamental Chemical Laws
Dalton’s Atomic Theory
Early Characterizations of Atoms
The Modern View of Atomic Structure
Molecules and Ions
Introduction to the Periodic Table
Naming Simple Compounds
