Chapter 2 Powerpoint Le

Basic ChemistryChapter 02

Basic ChemistryBasic Chemistry 2

OutlineOutline

Chemical ElementsChemical ElementsAtomsAtoms IsotopesIsotopesMolecules and CompoundsMolecules and Compounds

Chemical BondingChemical Bonding Ionic and CovalentIonic and CovalentHydrogenHydrogen

Properties of WaterProperties of Water

Acids and BasesAcids and Bases


Chemical ElementsChemical Elements

MatterMatter::Refers to anything that has mass and Refers to anything that has mass and occupies spaceoccupies space

Only 92 naturally occurring fundamental types Only 92 naturally occurring fundamental types of matter – 92 of matter – 92 ElementsElements

Organisms composed primarily (98%) of only Organisms composed primarily (98%) of only six elementssix elementsCarbon, Hydrogen, Nitrogen, Oxygen, Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, SulfurPhosphorus, Sulfur

CHNOPSCHNOPS

4Composition of Earth’s Crustversus Organisms


Atomic StructureAtomic Structure

Atoms - Smallest particles of elementsAtoms - Smallest particles of elementsAtoms composed of three types of subatomic Atoms composed of three types of subatomic

particlesparticlesProtonsProtons Positive chargePositive charge In nucleusIn nucleus

NeutronsNeutrons Neutral chargeNeutral charge Also found in nucleusAlso found in nucleus

ElectronsElectrons Negatively chargeNegatively charge Orbit nucleusOrbit nucleus


Each element represented by unique atomic Each element represented by unique atomic symbolsymbolOne or two lettersOne or two letters

First letter capitalizedFirst letter capitalized

Superscripted number before:Superscripted number before:

Represents mass numberRepresents mass number

Count of protons plus count of neutronsCount of protons plus count of neutrons

Subscripted number beforeSubscripted number before

Represents to atomic numberRepresents to atomic number

Number of protons in nucleusNumber of protons in nucleus

Atomic SymbolsAtomic Symbols

MassMassNumberNumber

AtomicAtomicNumberNumber

AtomicAtomicSymbolSymbol

126

Carbon

C


Periodic TablePeriodic Table

Elements grouped in periodic table based on Elements grouped in periodic table based on characteristicscharacteristicsVertical columns = groups; chemically similarVertical columns = groups; chemically similarHorizontal rows = periods; larger and largerHorizontal rows = periods; larger and larger

1

H1.008

3

Li6.941

11

Na22.99

19

K39.10

4

Be9.012

12

Mg24.31

20

Ca40.08

5

B10.81

13

Al26.98

21

Ga69.72

6

C12.01

14

Si28.09

22

Ge72.59

7

N14.01

15

P30.97

23

As74.92

8

O16.00

16

S32.07

24

Se78.96

9

F19.00

17

Cl35.45

25

Br79.90

10

Ne20.18

18

Ar39.95

26

Kr83.60

2

He4.003

II

IIII IIIIII IVIV VV VIVI VIIVII

VIIIVIII

11

22

33

44

Groups

Per

iod

s


Isotopes:Isotopes:

Atoms of the same element with a differing Atoms of the same element with a differing numbers of neutronsnumbers of neutrons

Some isotopes spontaneously decaySome isotopes spontaneously decay

RadioactiveRadioactive

Give off energy in the form of rays and Give off energy in the form of rays and subatomic particlessubatomic particles

Can be used as tracersCan be used as tracers

Mutagenic – Can cause cancerMutagenic – Can cause cancer

IsotopesIsotopes

126

Carbon 12C 13

6

Carbon 13C 14

6

Carbon 14C

9Some Medical Uses for

Low Level Radiation

10Some Medical Uses for

High Level Radiation

Basic ChemistryBasic Chemistry 11Electron Shells, OrbitalsElectron Shells, Orbitalsand Energy Levelsand Energy Levels

Atoms normally have as many electrons as Atoms normally have as many electrons as protonsprotons

Opposite charges balance leaving atom Opposite charges balance leaving atom neutralneutral

Electrons are attracted to the positive nucleusElectrons are attracted to the positive nucleusRevolve around nucleus in orbitalsRevolve around nucleus in orbitalsCan be pushed into higher orbitals with Can be pushed into higher orbitals with energyenergy

Release that energy when they fall back to Release that energy when they fall back to lower orbitallower orbital

Different energy levels referred to as electron Different energy levels referred to as electron shellsshells

Basic ChemistryBasic Chemistry 12The The Octet RuleOctet Rule for forDistribution of ElectronsDistribution of Electrons

Bohr modelsBohr models show show electron shellselectron shells as as concentric circles around nucleusconcentric circles around nucleus

Each shell has two or more Each shell has two or more electron orbitalselectron orbitals

Innermost shell has two orbitalsInnermost shell has two orbitals

Others have 8 or multiples thereofOthers have 8 or multiples thereof

Atoms with fewer than 8 electrons in Atoms with fewer than 8 electrons in outermost shell are chemically reactiveoutermost shell are chemically reactive

If 3 or less – Tendency to If 3 or less – Tendency to donatedonate electrons electrons

If 5 or more – Tendency to If 5 or more – Tendency to receivereceive electrons electrons

13Bohr Models of Atoms

14Periodic Table (Revisited)

Vertical columns indicatenumber of electronsin outermost shell

1

H1.008

3

Li6.941

11

Na22.99

19

K39.10

4

Be9.012

12

Mg24.31

20

Ca40.08

5

B10.81

13

Al26.98

21

Ga69.72

6

C12.01

14

Si28.09

22

Ge72.59

7

N14.01

15

P30.97

23

As74.92

8

O16.00

16

S32.07

24

Se78.96

9

F19.00

17

Cl35.45

25

Br79.90

10

Ne20.18

18

Ar39.95

26

Kr83.60

2

He4.003

1

2

3

4

Horizontal periods indicate

total number

of electron shells

I

II III IV V VI VII

VIII


Elements and CompoundsElements and Compounds

Molecule - Two or more atoms bonded Molecule - Two or more atoms bonded togethertogether If all atoms in molecule are of the same If all atoms in molecule are of the same elementelementMaterial is still an elementMaterial is still an element

OO22, H, H22, N, N22, etc., etc.

If at least one atom is from a different elementIf at least one atom is from a different elementMaterial formed is a compoundMaterial formed is a compound

COCO22, H, H22O, CO, C66HH1212OO66, etc., etc.

Characteristics dramatically different from Characteristics dramatically different from constituent elementsconstituent elements


Chemical BondingChemical Bonding

Bonds between atoms are caused by Bonds between atoms are caused by electrons in outermost shellselectrons in outermost shells

The process of bond formation is called a The process of bond formation is called a reactionreaction

The intensity of simple reactions can be The intensity of simple reactions can be predicted by the periodic tablepredicted by the periodic table

If two elements are horizontally close in the If two elements are horizontally close in the table, they usually react mildlytable, they usually react mildly

If they are horizontally far apart, they usually If they are horizontally far apart, they usually react vigorouslyreact vigorously

Basic ChemistryBasic Chemistry 17Types of Bonds:Types of Bonds:Ionic BondingIonic Bonding

Ionic BondsIonic BondsOctet ruleOctet rule::Atoms “want” 8 electrons in outer shellAtoms “want” 8 electrons in outer shell

If have < 4 outers, desire to donate themIf have < 4 outers, desire to donate them If have > 4 outers, desire to receive moreIf have > 4 outers, desire to receive more

Consider two elements from opposite ends Consider two elements from opposite ends of periodic tableof periodic table Element from right side:Element from right side:

Has 7 electrons in outer shellHas 7 electrons in outer shell ““Desperately wants” one more (7+1=8)Desperately wants” one more (7+1=8) Element from left side:Element from left side:

Has only 1 electron in outer shellHas only 1 electron in outer shell ““Desperately wants” to donate it (1-1=0=8)Desperately wants” to donate it (1-1=0=8)

Basic ChemistryBasic Chemistry 18Types of Bonds:Types of Bonds:Ionic Bond ExampleIonic Bond Example

Sodium:Sodium: From left endFrom left end Has 1 outer electronHas 1 outer electron

Chlorine:Chlorine: From right end of tableFrom right end of table Has 7 outer electronsHas 7 outer electrons

In reaction, Na completely gives up its outer In reaction, Na completely gives up its outer electron to Clelectron to Cl Na now a positive ion and Cl a negative ionNa now a positive ion and Cl a negative ion Dissimilar charges now bind ions togetherDissimilar charges now bind ions together Forms sodium chlorideForms sodium chloride An ionic compoundAn ionic compound NaCl table salt)NaCl table salt)

19Formation of Sodium Chloride

Basic ChemistryBasic Chemistry 20Types of Bonds:Types of Bonds:Covalent BondsCovalent Bonds

When atoms are horizontally closer together in the When atoms are horizontally closer together in the periodic tableperiodic table

The electrons are not permanently transferred from The electrons are not permanently transferred from one atom to the other like in NaClone atom to the other like in NaCl

A pair of electrons from the outer shell will “time A pair of electrons from the outer shell will “time share” with one atom and then the othershare” with one atom and then the other

This also causes the atoms to remain togetherThis also causes the atoms to remain together

Known as covalent bondingKnown as covalent bonding

Sometimes two par of electrons are shared between Sometimes two par of electrons are shared between atoms – a double covalent bondatoms – a double covalent bond

21Covalently Bonded Molecules


Nonpolar Covalent BondsNonpolar Covalent Bonds

Consider two elements that are equidistant Consider two elements that are equidistant from the edges of the periodic tablefrom the edges of the periodic tableAtoms will have about equal affinity for Atoms will have about equal affinity for electronselectrons One will “want” (with a specific intensity) to One will “want” (with a specific intensity) to donate electron(s)donate electron(s) The other will “want,” with the same intensity, The other will “want,” with the same intensity, to receive electron(s)to receive electron(s)

When bonded covalently:When bonded covalently: The bond electrons will spend about equal time The bond electrons will spend about equal time with both atomswith both atoms Such covalent bonds are said to be nonpolarSuch covalent bonds are said to be nonpolar


Polar Covalent BondsPolar Covalent Bonds

Consider two elements with one much closer to Consider two elements with one much closer to the edge of the table than the otherthe edge of the table than the other Atoms will have unequal affinity for electronsAtoms will have unequal affinity for electrons One will “want” (with a specific intensity) to donate One will “want” (with a specific intensity) to donate

or receive electron(s)or receive electron(s) The other will “want” (with a The other will “want” (with a differentdifferent intensity) to intensity) to

donate or receive electron(s)donate or receive electron(s)

When bonded covalently:When bonded covalently: The bond electrons will spend more time with one The bond electrons will spend more time with one atom than the otheratom than the other The atom that gets the most time with the electrons The atom that gets the most time with the electrons

will be slightly negativewill be slightly negative The other will be slightly positiveThe other will be slightly positive

Such covalent bonds are said to be polarSuch covalent bonds are said to be polar

Basic ChemistryBasic Chemistry 24Types of Bonds:Types of Bonds:Hydrogen BondsHydrogen Bonds

Water (HWater (H22O or H–O–H) is a polar moleculeO or H–O–H) is a polar molecule

Electrons spend more time with O than H’sElectrons spend more time with O than H’s

H’s become slightly H’s become slightly ++, O slightly , O slightly ––

When polar molecules are dissolved in waterWhen polar molecules are dissolved in water

The H’s of water molecules are attracted to the The H’s of water molecules are attracted to the negative parts of the solute moleculesnegative parts of the solute molecules

Results in a weak bond Results in a weak bond – – the hydrogen bondthe hydrogen bond

Easily broken, but many together can be quite Easily broken, but many together can be quite strongstrong

25Water Molecule

26Hydrogen Bonding

Basic ChemistryBasic Chemistry 27The Chemistry of Water:The Chemistry of Water:Heat CapacityHeat Capacity

Water has a high heat capacityWater has a high heat capacity Temperature = rate of vibration of moleculesTemperature = rate of vibration of molecules Apply heat to liquidApply heat to liquid Molecules bounce fasterMolecules bounce faster Increases temperatureIncreases temperature

But, when heat applied to waterBut, when heat applied to water Hydrogen bonds restrain bouncingHydrogen bonds restrain bouncing Temperature rises more slowly per unit heatTemperature rises more slowly per unit heat Water at a given temp. has more heat than most liquidsWater at a given temp. has more heat than most liquids

Thermal inertiaThermal inertia – resistance to temperature change – resistance to temperature change More heat required to raise water one degree than most More heat required to raise water one degree than most

other liquids (1 calorie per gram)other liquids (1 calorie per gram) Also, more heat is extracted/released when lowering Also, more heat is extracted/released when lowering

water one degree than most other liquidswater one degree than most other liquids

Basic ChemistryBasic Chemistry 28Properties of Water:Properties of Water:Heat of VaporizationHeat of Vaporization

High heat of vaporizationHigh heat of vaporization

To raise water from 98 to 99 ºC; ~1 calorieTo raise water from 98 to 99 ºC; ~1 calorie

To raise water from 99 to 100 ºC; ~1 calorieTo raise water from 99 to 100 ºC; ~1 calorie

However, large numbers of hydrogen bonds must be However, large numbers of hydrogen bonds must be broken to evaporate waterbroken to evaporate water

To raise water from 100 to 101 ºC; ~540 calories!To raise water from 100 to 101 ºC; ~540 calories!

This is why sweating (and panting) coolsThis is why sweating (and panting) cools

Evaporative cooling is best when humidity is low Evaporative cooling is best when humidity is low because evaporation occurs rapidlybecause evaporation occurs rapidly

Evaporative cooling works poorest when humidity is Evaporative cooling works poorest when humidity is high because evaporation occurs slowlyhigh because evaporation occurs slowly

29Evaporative Cooling

of Animals

Basic ChemistryBasic Chemistry 30Properties of Water:Properties of Water:Heat of FusionHeat of Fusion

Heat of fusion (melting)Heat of fusion (melting)To raise ice from -2 to -1 ºC; ~1 calorieTo raise ice from -2 to -1 ºC; ~1 calorieTo raise water from -1 to 0 ºC; ~1 calorieTo raise water from -1 to 0 ºC; ~1 calorieTo raise water from 0 to 1 ºC; ~80 calories!To raise water from 0 to 1 ºC; ~80 calories!

This is why ice at 0 ºC keeps stuff cold MUCH This is why ice at 0 ºC keeps stuff cold MUCH longer than water at 1 ºClonger than water at 1 ºC

This is why ice is used for coolingThis is why ice is used for coolingNOT because ice is coldNOT because ice is coldBut because it absorbs so much heat before it But because it absorbs so much heat before it will warm by one degreewill warm by one degree

31Heat Content of Waterat Various Temperatures

Basic ChemistryBasic Chemistry 32Properties of Water:Properties of Water:Water as a SolventWater as a Solvent

Solutions consist of:Solutions consist of: A A solventsolvent (the most abundant part) and (the most abundant part) and A A solutesolute (less abundant part) that is dissolved in (less abundant part) that is dissolved in the solventthe solvent

Polar compounds readily dissolve; Polar compounds readily dissolve; hydrophilichydrophilicNonpolar compounds dissolve only slightly; Nonpolar compounds dissolve only slightly;

hydrophobichydrophobicIonic compounds dissociate in waterIonic compounds dissociate in water

NaNa++

Attracted to negative (O) end of HAttracted to negative (O) end of H22OO Each NaEach Na++ completely surrounded by H completely surrounded by H22OO

ClCl--

Attracted to positive (HAttracted to positive (H22) end of H) end of H22OO Each ClEach Cl-- completely surrounded by H completely surrounded by H22OO

Basic ChemistryBasic Chemistry 33Properties of Water:Properties of Water:Uniqueness of IceUniqueness of Ice

Frozen water less dense than liquid waterFrozen water less dense than liquid water

Otherwise, oceans and deep lakes would fill Otherwise, oceans and deep lakes would fill with ice from the bottom upwith ice from the bottom up

Ice acts as an insulator on top of a frozen Ice acts as an insulator on top of a frozen body of waterbody of water

Melting ice draws heat from the environmentMelting ice draws heat from the environment

34Density of Waterat Various Temperatures

35A Pond in Winter

36Water as a Transport Medium

Basic ChemistryBasic Chemistry 37Properties of Water:Properties of Water:Cohesion & AdhesionCohesion & Adhesion

Cohesive and AdhesiveCohesive and Adhesive CohesionCohesion – Hydrogen bonds hold water molecules – Hydrogen bonds hold water molecules

tightly togethertightly together AdhesionAdhesion – Hydrogen bonds for between water and – Hydrogen bonds for between water and

other polar materialsother polar materials Allow water be drawn many meters up a tree in a Allow water be drawn many meters up a tree in a

tubular vesseltubular vessel

High High Surface TensionSurface Tension Water molecules at surface hold more tightly than Water molecules at surface hold more tightly than

below surfacebelow surface Amounts to an invisible “skin” on water surfaceAmounts to an invisible “skin” on water surface Allows small nonpolar objects (like water strider) to Allows small nonpolar objects (like water strider) to

sit on top of watersit on top of water

Basic ChemistryBasic Chemistry 38pH of Water:pH of Water:AcidsAcids

AcidsAcids

Dissociate in water and release Dissociate in water and release hydrogen ions (Hhydrogen ions (H++))

Sour to tasteSour to taste

Hydrochloric acid (stomach acid) is a Hydrochloric acid (stomach acid) is a gas with symbol HClgas with symbol HCl

In water, it dissociates into HIn water, it dissociates into H++ and Cl and Cl--

Dissociation of HCl is almost total, therefore Dissociation of HCl is almost total, therefore it is a strong acidit is a strong acid

Basic ChemistryBasic Chemistry 39pH of Water:pH of Water:BasesBases

BasesBases::

Either take up hydrogen ions (HEither take up hydrogen ions (H++) or ) or release hydroxide ions (OHrelease hydroxide ions (OH--))

Bitter to tasteBitter to taste

Sodium hydroxide (drain cleaner) is a Sodium hydroxide (drain cleaner) is a solid with symbol NaOHsolid with symbol NaOH

In water, it dissociates into NaIn water, it dissociates into Na++ and OH and OH--

Dissociation of NaOH is almost total, Dissociation of NaOH is almost total, therefore it is a strong basetherefore it is a strong base


pH ScalepH Scale

pH scale used to indicate acidity and alkalinity pH scale used to indicate acidity and alkalinity of a solution.of a solution.Values range from 0-14Values range from 0-14 0 to <7 = Acidic0 to <7 = Acidic 7 = Neutral7 = Neutral >7 to 14 = Basic (or alkaline)>7 to 14 = Basic (or alkaline)

Logarithmic ScaleLogarithmic Scale Each unit change in pH represents a change of Each unit change in pH represents a change of 10X10X pH of 4 is 10X as acidic as pH of 5pH of 4 is 10X as acidic as pH of 5 pH of 10 is 100X more basic than pH of 8pH of 10 is 100X more basic than pH of 8

41The pH Scale


Buffers and pHBuffers and pH

When HWhen H++ is added to pure water at pH 7, pH is added to pure water at pH 7, pH goes down and water becomes acidicgoes down and water becomes acidic

When OHWhen OH-- is added to pure water at pH 7, pH is added to pure water at pH 7, pH goes up and water becomes alkalinegoes up and water becomes alkaline

Buffers are solutes in water that resist change Buffers are solutes in water that resist change in pHin pH

When HWhen H++ is added, buffer may absorb, or is added, buffer may absorb, or counter by adding OHcounter by adding OH--

When OHWhen OH-- is added, buffer may absorb, or is added, buffer may absorb, or counter by adding Hcounter by adding H++


Buffers in BiologyBuffers in Biology

Health of organisms requires maintaining pH Health of organisms requires maintaining pH of body fluids within narrow limitsof body fluids within narrow limits

Human blood normally 7.4 (slightly alkaline)Human blood normally 7.4 (slightly alkaline)

Many foods and metabolic processes add or Many foods and metabolic processes add or subtract Hsubtract H+ + oror OHOH-- ions ions

Reducing blood pH to 7.0 results in acidosisReducing blood pH to 7.0 results in acidosis

Increasing blood pH to 7.8 results in alkalosisIncreasing blood pH to 7.8 results in alkalosis

Both life threatening situationsBoth life threatening situations

Bicarbonate ion (Bicarbonate ion (--HCOHCO33) in blood buffers pH to ) in blood buffers pH to 7.47.4


ReviewReview

Chemical ElementsChemical ElementsAtomsAtoms IsotopesIsotopesMolecules and CompoundsMolecules and Compounds

Chemical BondingChemical Bonding Ionic and CovalentIonic and CovalentHydrogenHydrogen

Properties of WaterProperties of Water

Acids and BasesAcids and Bases

Basic ChemistryEnding Slide Chapter 02

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