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KTT 111/3 – Inorganic Chemistry I

Dr. Farook Adam

August 2005

Chapter 1: Atoms and ElementsChapter 1: Atoms and Elements

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Chapter 1: Atoms and ElementsChapter 1: Atoms and Elements ChemistryChemistry is a is a sciencescience that studies the that studies the

composition and properties of mattercomposition and properties of matter Matter Matter isis anything that takes up space anything that takes up space

and has and has massmass Mass is a measure of the amount of Mass is a measure of the amount of

matter in a samplematter in a sample Chemistry holds a unique place among the Chemistry holds a unique place among the

sciences because all things are composed sciences because all things are composed of chemicalsof chemicals

A knowledge of chemistry will be valuable A knowledge of chemistry will be valuable whatever branch of science you studywhatever branch of science you study

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Chemistry is constantly changing as new Chemistry is constantly changing as new discoveries are made by researchersdiscoveries are made by researchers

Researchers use a commonsense approach to Researchers use a commonsense approach to the study of natural phenomena called the the study of natural phenomena called the scientific methodscientific method

A scientific study normally:A scientific study normally: Begins with a question about natureBegins with a question about nature Involves a search of the work of othersInvolves a search of the work of others Requires observing the results of experimentsRequires observing the results of experiments Often results in a conclusion, or a statement based Often results in a conclusion, or a statement based

on what is thought about a series of observationson what is thought about a series of observations

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Experiments provide empirical factsExperiments provide empirical facts Facts are called dataFacts are called data A broad generalization based on the A broad generalization based on the

results of many experiments is called a results of many experiments is called a ((scientific) lawscientific) law

Laws are often expressed as mathematical Laws are often expressed as mathematical equations equations

Laws summarize the results of experimentsLaws summarize the results of experiments

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Theoretical models attempt to explain why Theoretical models attempt to explain why substances behave as they dosubstances behave as they do

A A hypothesishypothesis is a tentative explanation is a tentative explanation A A theorytheory is an experimentally tested explanation of is an experimentally tested explanation of

the behavior of naturethe behavior of nature

The scientific method is dynamic: observations lead to laws, whichsuggest new experiments, which may lead to or change a hypothesis,which may produce a theory.

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Chemical substances are comprised of Chemical substances are comprised of atomsatoms

Atoms combine to form Atoms combine to form moleculesmolecules which can be represented in a number which can be represented in a number of ways, including:of ways, including:

(a) Using chemical symbols and lines for “connections”

(b) A 3-D ball-and-stick model

(c) A 3-D space-filling model

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Characteristics or Characteristics or properties properties of of materials distinguish one type of materials distinguish one type of substance from anothersubstance from another

Properties can be classified as Properties can be classified as physical physical or or chemicalchemical Physical properties can be observed Physical properties can be observed

without changing the chemical makeup of without changing the chemical makeup of the substancethe substance

Chemical properties involve a chemical Chemical properties involve a chemical change and result in change and result in differentdifferent substances substances

Chemical changes are described by Chemical changes are described by chemical reactionschemical reactions

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Properties can also be described as Properties can also be described as intensiveintensive or or extensiveextensive Intensive properties are independent of Intensive properties are independent of

sample sizesample size• Examples: sample color and melting pointExamples: sample color and melting point

Extensive properties depend on sample Extensive properties depend on sample sizesize• Examples: sample volume and massExamples: sample volume and mass

In general, intensive properties are In general, intensive properties are more useful in identifying a substancemore useful in identifying a substance

Matter is often classified by propertiesMatter is often classified by properties

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The three common physical states of matter The three common physical states of matter have different properties:have different properties:

Solids have a fixed shape and volumeSolids have a fixed shape and volume• Particles are close together and have restricted motionParticles are close together and have restricted motion

Liquids have indefinite shape but fixed volumeLiquids have indefinite shape but fixed volume• Particles are close together but are able to flowParticles are close together but are able to flow

Gases have indefinite shape and volumeGases have indefinite shape and volume• Particles are separated by lots of empty spaceParticles are separated by lots of empty space

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ElementsElements are substances that cannot are substances that cannot be decomposed by chemical means into be decomposed by chemical means into simpler substancessimpler substances

Each element is assigned a unique Each element is assigned a unique chemical symbolchemical symbol Most are one or two lettersMost are one or two letters First letter is always capitalizedFirst letter is always capitalized All remaining letters are lowercaseAll remaining letters are lowercase Names and chemical symbols of the Names and chemical symbols of the

elements are listed on the inside front elements are listed on the inside front cover of the bookcover of the book

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Compounds are substances formed from Compounds are substances formed from two or more two or more differentdifferent elements combined elements combined in a fixed proportion by massin a fixed proportion by mass

The physical and chemical properties of The physical and chemical properties of a compound are, in general, different a compound are, in general, different than the physical and chemical than the physical and chemical properties of the elements of which it is properties of the elements of which it is comprisedcomprised

Elements and compounds are examples Elements and compounds are examples of of pure substances pure substances whose composition whose composition is the same, regardless of sourceis the same, regardless of source

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A A mixturemixture consists of varying amounts consists of varying amounts of two or more elements or compoundsof two or more elements or compounds Homogeneous mixturesHomogeneous mixtures or or solutionssolutions

have the same properties throughout the have the same properties throughout the samplesample

Heterogeneous mixtures Heterogeneous mixtures consist of two or consist of two or more phasesmore phases

Matter can be classified:Matter can be classified:

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TutorialTutorialAnda boleh daftar di bilik 015A Pudat Anda boleh daftar di bilik 015A Pudat

Pengajian Sains Kimia mulai hari ini!!!Pengajian Sains Kimia mulai hari ini!!!

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We take for granted the existence of We take for granted the existence of atoms and moleculesatoms and molecules

The concept of the atom had limited The concept of the atom had limited scientific usefulness until the discovery scientific usefulness until the discovery of two important laws: the of two important laws: the Law of Law of conservation of mass conservation of mass andand the Law of the Law of Definite ProportionsDefinite Proportions

These laws summarized the results of These laws summarized the results of the experimental observations of many the experimental observations of many scientistsscientists

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Law of Conservation of Mass:Law of Conservation of Mass: No detectable gain or loss of mass occurs No detectable gain or loss of mass occurs

in chemical reactions. Mass is conserved.in chemical reactions. Mass is conserved. Law of Definite Proportions:Law of Definite Proportions:

In a given chemical compound, the In a given chemical compound, the elements are always combined in the same elements are always combined in the same proportions by mass.proportions by mass.

In the sciences mass is measured in In the sciences mass is measured in units of units of gramsgrams (symbol, (symbol, gg)) One pound equals 453.6 g One pound equals 453.6 g

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The laws of conservation of mass and The laws of conservation of mass and definite proportions provided the definite proportions provided the experimental foundationexperimental foundation for the for the atomic atomic theorytheory

Dalton’s Atomic Theory (~1803 AD):Dalton’s Atomic Theory (~1803 AD):• Matter consists of tiny particles called atoms.Matter consists of tiny particles called atoms.• Atoms are indestructible. In chemical reactions, the Atoms are indestructible. In chemical reactions, the

atoms rearrange but they do not themselves break atoms rearrange but they do not themselves break apart.apart.

• In any sample of a pure element, all the atoms are In any sample of a pure element, all the atoms are identical in mass and other properties.identical in mass and other properties.

• The atoms of different elements differ in mass and The atoms of different elements differ in mass and other properties.other properties.

• In a given compound the constituent atoms are always In a given compound the constituent atoms are always present in the same fixed present in the same fixed numerical numerical ratio.ratio.

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Support for Dalton’s Atomic Theory: The Law of Multiple Proportions Whenever two elements form more than one compound, the different masses of one element that combine with the same mass of the other element are in the ratio of small whole numbers.

Each molecule has one sulfur atom, and therefore the same mass of sulfur. The oxygen ratio is 3 to 2 by both mass and atoms:

Sample experimental data: Mass Mass Compound Size S OSulfur dioxide 2.00 g 1.00 g 1.00 gSulfur trioxide 2.50 g 1.00 g 1.50 g

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It follows from Dalton’s Atomic Theory that It follows from Dalton’s Atomic Theory that atoms of an element have a constant, atoms of an element have a constant, characteristic characteristic atomic massatomic mass or or atomic weightatomic weight

For example, for For example, for anyany sample of hydrogen sample of hydrogen fluoride:fluoride:

• F-to-H atom ratio: 1 to 1F-to-H atom ratio: 1 to 1• F-to-H mass ratio: 19.0 to 1.00F-to-H mass ratio: 19.0 to 1.00

This is only possible if each fluorine atom is 19.0 This is only possible if each fluorine atom is 19.0 times heavier than each hydrogen atomtimes heavier than each hydrogen atom

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It turns out that most elements in nature It turns out that most elements in nature are are uniformuniform mixtures of two or more mixtures of two or more kinds of atoms with slightly different kinds of atoms with slightly different massesmasses

Atoms of the same element with Atoms of the same element with different masses are called different masses are called isotopesisotopes

• For example: there are 3 isotopes of hydrogen For example: there are 3 isotopes of hydrogen and 4 isotopes of ironand 4 isotopes of iron

Chemically, isotopes have virtually Chemically, isotopes have virtually identical chemical propertiesidentical chemical properties

The relative proportions of the different The relative proportions of the different isotopes are essentially constantisotopes are essentially constant

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A uniform mass scale for atoms requires a A uniform mass scale for atoms requires a standardstandard

For For atomic mass unitsatomic mass units (amu, given the (amu, given the symbol symbol uu) the standard is based on carbon:) the standard is based on carbon:

• 1 atom of carbon-12 = 12 u (exactly)1 atom of carbon-12 = 12 u (exactly)• 1 u = 1/12 the mass of 1 atom of carbon-12 (exactly)1 u = 1/12 the mass of 1 atom of carbon-12 (exactly)

This definition results in the assignment of This definition results in the assignment of approximately 1 u for the mass of hydrogen approximately 1 u for the mass of hydrogen (the lightest atom)(the lightest atom)

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Example: Naturally occurring chlorine is a Example: Naturally occurring chlorine is a mixture of two isotopes. In every sample of this mixture of two isotopes. In every sample of this element, 75.77% of the atoms are chlorine-35 element, 75.77% of the atoms are chlorine-35 and 24.23% are chlorine-37. The measured and 24.23% are chlorine-37. The measured mass of chlorine-35 is 34.9689 u and that of mass of chlorine-35 is 34.9689 u and that of chlorine-37 is 36.9659 u. Calculate the average chlorine-37 is 36.9659 u. Calculate the average atomic mass of chlorine.atomic mass of chlorine.

Abundance Mass

Isotope (%) (u) Contribution

Chlorine-35 75.77 34.9689 0.7577 * 34.9689 = 26.50 u Chlorine-37 24.23 36.9659 0.2423 * 36.9659 = 8.957 u (Rounded) Total = 35.46 u

The average mass of 1 atom of chlorine in nature is 35.46 u.

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Experiments have been performed that Experiments have been performed that show atoms are comprised of show atoms are comprised of subatomic particlessubatomic particles

There are three principal kinds of There are three principal kinds of subatomic particles:subatomic particles:

• Proton – carries a positive charge, found in the Proton – carries a positive charge, found in the nucleusnucleus

• Electron – carries a negative charge, found Electron – carries a negative charge, found outside the nucleus, about 1/1800 the mass of a outside the nucleus, about 1/1800 the mass of a protonproton

• Neutron – carries no charge, found in the Neutron – carries no charge, found in the nucleus, a bit heavier than a proton, about 1800 nucleus, a bit heavier than a proton, about 1800 times heavier than an electrontimes heavier than an electron

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An element can be defined as a An element can be defined as a substance whose atoms all contain the substance whose atoms all contain the identical number of protons, called the identical number of protons, called the atomic numberatomic number ( (ZZ) )

Isotopes are distinguished by Isotopes are distinguished by mass mass number number ((AA):):

• Atomic number, Z = number of protonsAtomic number, Z = number of protons• Mass number, A = (number of protons) + Mass number, A = (number of protons) +

(number of neutrons)(number of neutrons) For charge neutrality, the number of For charge neutrality, the number of

electrons and protons must be equalelectrons and protons must be equal

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This information can be summarizedThis information can be summarized Example: For uranium-235Example: For uranium-235

• Number of protons = 92 ( = number of Number of protons = 92 ( = number of electrons)electrons)

• Number of neutrons = 143Number of neutrons = 143• Atomic number (Z) = 92Atomic number (Z) = 92• Mass number (A) = 92 + 143 = 235Mass number (A) = 92 + 143 = 235• Chemical symbol = UChemical symbol = U

Summary for uranium-235:Summary for uranium-235:

Mass number, A (protons + neutrons) Chemical Symbol Atomic number, Z (number of protons)

235 U 92

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The The Periodic TablePeriodic Table summarizes chemical and physical summarizes chemical and physical properties of the elementsproperties of the elements

The first Periodic Tables were arranged by increasing The first Periodic Tables were arranged by increasing atomic massatomic mass

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Dmitri Mendeleev(Rusia)

Julius Lothar Meyer(German)

Both these researchers drew out the first periodic table independently of each other.

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Mendeleev have been honored as the first person to arrange the elements in the form of a table because he reported his findings to the Russian Chemical Society a few months earlier than Meyer!!!!

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The Modern Periodic table is The Modern Periodic table is arranged by increasing atomic arranged by increasing atomic number:number:

Elements are arranged in Elements are arranged in numbered numbered rowsrows called called periodsperiods

The vertical columns are called The vertical columns are called groupsgroups or families (group or families (group labels vary)labels vary)

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Modern Periodic Table with group labels Modern Periodic Table with group labels and chemical families identifiedand chemical families identified

Note: Placement of elements 58 – 71 and 90 – 103 saves space

Lanthanides

Actinides

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Some important classifications:Some important classifications: A groups = A groups = representative elementsrepresentative elements or or main group main group

elementselements

I A = alkali metalsI A = alkali metals II A = alkaline earth metalsII A = alkaline earth metals VII A = halogensVII A = halogens VIII = noble gasesVIII = noble gases

B groups = B groups = transition elementstransition elements Inner transition elements = elements 58 – 71 and Inner transition elements = elements 58 – 71 and

90 – 10390 – 103

58 – 71 = lanthanide elements58 – 71 = lanthanide elements 90 – 103 = actinide elements90 – 103 = actinide elements

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Classification as metals, nonmetals, and Classification as metals, nonmetals, and metalloidsmetalloids

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MetalsMetals• Tend to shine (have Tend to shine (have metallic lustermetallic luster))• Can be hammered or rolled into thin sheets Can be hammered or rolled into thin sheets

((malleable) malleable) andand can be drawn into wire can be drawn into wire ((ductileductile))

• Are solids at room temperature and conduct Are solids at room temperature and conduct electricityelectricity

NonmetalsNonmetals• Lack the properties of metalsLack the properties of metals• React with metals to form (ionic) compoundsReact with metals to form (ionic) compounds

MetalloidsMetalloids• Have properties between metals and Have properties between metals and

nonmetalsnonmetals

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The EndThe End

Do the exercises at the end of chapter ONE.Do the exercises at the end of chapter ONE.For your own practice only!!For your own practice only!!

You do not have to pass up this assignment.You do not have to pass up this assignment.

Any questions?