basic chemistry chapter 02. basic chemistry 2outline chemical elements atoms isotopes molecules...
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Basic ChemistryChapter 02
2Basic ChemistryBasic Chemistry
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
3Basic ChemistryBasic Chemistry
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
5Basic ChemistryBasic Chemistry
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
6Basic ChemistryBasic Chemistry
Atomic SymbolsAtomic Symbols
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
MassMassNumberNumber
AtomicAtomicNumberNumber
AtomicAtomicSymbolSymbol
126
Carbon
C
7Basic ChemistryBasic Chemistry
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
Periods
8Basic ChemistryBasic Chemistry
IsotopesIsotopes
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
126
Carbon 12C 13
6
Carbon 13C 14
6
Carbon 14C
9Some Medical Uses forLow Level Radiation
10Some Medical Uses forHigh Level Radiation
11Basic 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
12Basic 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 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
15Basic ChemistryBasic Chemistry
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
16Basic 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 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
17Basic ChemistryBasic ChemistryTypes 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)
18Basic ChemistryBasic ChemistryTypes 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
20Basic 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 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
22Basic 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 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
23Basic ChemistryBasic Chemistry
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
24Basic 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 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
27Basic ChemistryBasic ChemistryThe 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
28Basic 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
29Evaporative Cooling
of Animals
30Basic ChemistryBasic ChemistryProperties 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
32Basic 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 (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
33Basic 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
34Density of Waterat Various Temperatures
35A Pond in Winter
36Water as a Transport Medium
37Basic ChemistryBasic ChemistryProperties 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
38Basic ChemistryBasic ChemistrypH 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
39Basic 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 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
40Basic 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
41The pH Scale
42Basic 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
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++
43Basic ChemistryBasic Chemistry
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
44Basic ChemistryBasic Chemistry
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