Download - Ch. 2 Outline
1Basic ChemistryBasic Chemistry
Ch. 2 OutlineCh. 2 Outline
Basic ChemistryBasic Chemistry
2Basic ChemistryBasic Chemistry
Chemical ElementsChemical Elements
MatterMatter::Anything that has mass and occupies spaceAnything that has mass and occupies spaceOnly 92 naturally occurring Only 92 naturally occurring elementselements
Organisms composed primarily (95%) of only Organisms composed primarily (95%) of only six elementssix elementsCarbon, Hydrogen, Nitrogen, Oxygen, Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, SulfurPhosphorus, Sulfur
CHNOPSCHNOPS
3
Composition of Earth’s Crustversus Organisms
4Basic ChemistryBasic Chemistry
Atomic StructureAtomic Structure
AtomsAtoms - Smallest particles of elements - 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 Negative chargeNegative charge Orbit nucleusOrbit nucleus
5Basic ChemistryBasic Chemistry
Atomic SymbolsAtomic Symbols
Each element represented by unique atomic Each element represented by unique atomic symbolsymbolFirst letter capitalizedFirst letter capitalizedSuperscripted numberSuperscripted number:: Represents mass numberRepresents mass number Count of protons plus count of neutronsCount of protons plus count of neutrons
Subscripted numberSubscripted number:: Represents atomic numberRepresents atomic number Number of protons in nucleusNumber of protons in nucleus
MassMassNumberNumber
AtomicAtomicNumberNumber
AtomicAtomicSymbolSymbol
126
Carbon
C
6Basic ChemistryBasic Chemistry
Periodic TablePeriodic TableElements grouped in periodic table based on Elements grouped in periodic table based on characteristicscharacteristicsVertical columns = groups; chemically similarVertical columns = groups; chemically similar
1
H1.0083
Li6.94111
Na22.9919
K39.10
4
Be9.01212
Mg24.3120
Ca40.08
5
B10.8113
Al26.9821
Ga69.72
6
C12.0114
Si28.0922
Ge72.59
7
N14.0115
P30.9723
As74.92
8
O16.0016
S32.0724
Se78.96
9
F19.0017
Cl35.4525
Br79.90
10
Ne20.1818
Ar39.9526
Kr83.60
2
He4.003
II
IIII IIIIII IVIV VV VIVI VIIVII
VIIIVIII11
22
33
44
Groups
Periods
7Basic ChemistryBasic Chemistry
IsotopesIsotopesIsotopesIsotopes::
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 tracersMutagenicMutagenic – Can cause cancer – Can cause cancer
126
Carbon 12C 13
6Carbon 13
C 146
Carbon 14C
8Some Medical Uses forLow Level Radiation
9Some Medical Uses forHigh Level Radiation
10Basic ChemistryBasic ChemistryElectron 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
11Basic ChemistryBasic ChemistryThe 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 nucleusEach 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
12Bohr Models of Atoms
13Periodic Table (Revisited)
Vertical columns indicatenumber of electronsin outermost shell
1
H1.0083
Li6.94111
Na22.9919
K39.10
4
Be9.01212
Mg24.3120
Ca40.08
5
B10.8113
Al26.9821
Ga69.72
6
C12.0114
Si28.0922
Ge72.59
7
N14.0115
P30.9723
As74.92
8
O16.0016
S32.0724
Se78.96
9
F19.0017
Cl35.4525
Br79.90
10
Ne20.1818
Ar39.9526
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
14Basic ChemistryBasic Chemistry
Elements and CompoundsElements and CompoundsMoleculeMolecule - Two or more atoms bonded - Two or more atoms bonded together by covalent bondstogether by covalent bonds 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 Material formed is a compoundcompound COCO22, H, H22O, CO, C66HH1212OO66, etc., etc. Characteristics dramatically different from Characteristics dramatically different from constituent elementsconstituent elements
15Basic ChemistryBasic Chemistry
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 chemical reactionchemical reaction
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
16Basic ChemistryBasic ChemistryTypes of Bonds:Types of Bonds:Ionic BondingIonic Bonding
Sodium:Sodium:Has 1 outer electronHas 1 outer electron
Chlorine:Chlorine:Has 7 outer electronsHas 7 outer electrons
In reaction, Na completely gives up its In reaction, Na completely gives up its outer electron to Clouter electron to ClNa now a positive ion and Cl a negative ionNa now a positive ion and Cl a negative ionDissimilar charges now bind ions togetherDissimilar charges now bind ions togetherForms sodium chlorideForms sodium chlorideAn An ionic compoundionic compoundNaCl table salt)NaCl table salt)
17Formation of Sodium Chloride
18Basic ChemistryBasic ChemistryTypes 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 Known as covalent bondingcovalent bonding
Sometimes two pairs of electrons are shared Sometimes two pairs of electrons are shared between atoms – a between atoms – a double covalent bonddouble covalent bond
19Covalently Bonded Molecules
20Basic ChemistryBasic Chemistry
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
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 Such covalent bonds are said to be nonpolarnonpolar
21Basic ChemistryBasic Chemistry
Polar Covalent BondsPolar Covalent Bonds
Consider two elements with one much Consider two elements with one much closer to the edge of the table than the closer to the edge of the table than the otherotherAtoms will have unequal affinity for Atoms will have unequal affinity for electronselectrons
The bond electrons will spend more time The bond electrons will spend more time with one atom than the otherwith one atom than the other The atom that gets the most time with the The atom that gets the most time with the electrons will be slightly negativeelectrons will be slightly negative The other will be slightly positiveThe other will be slightly positive
Such covalent bonds are said to be Such covalent bonds are said to be polarpolar
22Basic ChemistryBasic ChemistryTypes 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 moleculeElectrons spend more time with O than H’sElectrons spend more time with O than H’sH’s become slightly H’s become slightly ++, O slightly , O slightly ––
When polar molecules are dissolved in waterWhen polar molecules are dissolved in waterThe 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 the hydrogen bondhydrogen bondEasily broken, but many together can be quite Easily broken, but many together can be quite strongstrong
23Water Molecule
24Hydrogen Bonding
25Basic ChemistryBasic ChemistryThe Chemistry of Water:The Chemistry of Water:Heat CapacityHeat Capacity
Water has a high heat capacityWater has a high heat capacity TemperatureTemperature = rate of vibration of molecules = 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
26Basic ChemistryBasic ChemistryProperties 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
27Evaporative Cooling
of Animals
28Basic ChemistryBasic ChemistryProperties of Water:Properties of Water:Heat of FusionHeat of Fusion
Heat of fusionHeat of fusion (melting) (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 coolingNOTNOT because ice is cold 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
29Heat Content of Waterat Various Temperatures
30Basic ChemistryBasic ChemistryProperties 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 the (less abundant part) that is dissolved in the solventsolvent
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
31Basic ChemistryBasic ChemistryProperties 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
32Density of Waterat Various Temperatures
33A Pond in Winter
34Basic ChemistryBasic ChemistryProperties of Water:Properties of Water:Cohesion & AdhesionCohesion & Adhesion
CohesionCohesion – Hydrogen bonds hold water – Hydrogen bonds hold water molecules tightly togethermolecules tightly together
AdhesionAdhesion – Hydrogen bonds for between water – Hydrogen bonds for between water and other polar materialsand other polar materials
Allows water be drawn many meters up a tree in a Allows 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) Allows small nonpolar objects (like water strider) to sit on top of waterto sit on top of water
35Water as a Transport Medium
36Basic ChemistryBasic ChemistrypH of Water:pH of Water:AcidsAcids
AcidsAcidsDissociate in water and release Dissociate in water and release hydrogen ions (Hhydrogen ions (H++))
Sour to tasteSour to tasteHydrochloric 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
37Basic ChemistryBasic ChemistrypH 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 tasteSodium 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
38Basic ChemistryBasic Chemistry
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
39The pH Scale
40Basic ChemistryBasic Chemistry
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
BuffersBuffers are solutes in water that resist change are solutes in water that resist change in pHin pHWhen 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++
41Basic ChemistryBasic Chemistry
Buffers in BiologyBuffers in BiologyHealth of organisms requires maintaining pH Health of organisms requires maintaining pH of body fluids within narrow limitsof body fluids within narrow limitsHuman 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