Ap Bio Ch2 PowerPoint

Chapter 2

Atoms, Atoms, Molecules,Molecules,

and Lifeand Life

Chapter 2 2

Covalent bond Covalent bond — electrons shared— electrons shared• Shared unequally — Shared unequally — polarpolar• Shared equally — Shared equally — nonpolarnonpolar

Ionic bondIonic bond — electron transfers total # — electron transfers total #• Both atoms Both atoms ionizedionized• May May dissociatedissociate in water in water

Chemical BondingChemical Bonding

Chapter 2 3

Bonding Involves ElectronsBonding Involves Electrons

One pair electrons per bondOne pair electrons per bondOuter electrons form bondsOuter electrons form bondsBehave using “Behave using “octet ruleoctet rule””If nearly eight in outer shellIf nearly eight in outer shell

• Desires more electronsDesires more electrons• OxidizerOxidizer

If less than four in outer shellIf less than four in outer shell• Desires fewer electronsDesires fewer electrons• ReducerReducer

Chapter 2 4ƒ2-4a&b

Most Elements MolecularMost Elements Molecular

(a) In hydrogen gas, one electron from each hydrogen atom is shared, forming a single covalent bond. The resulting molecule of hydrogen gas is represented as H–H or H2.

(a) In hydrogen gas, one electron from each hydrogen atom is shared, forming a single covalent bond. The resulting molecule of hydrogen gas is represented as H–H or H2.

(b) In oxygen gas, two oxygen atoms share four electrons, forming a double bond(O=O or O2).

(b) In oxygen gas, two oxygen atoms share four electrons, forming a double bond(O=O or O2).

Chapter 2 5ƒ2-3a,b

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Ionic Bonding in NaClIonic Bonding in NaCl

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SodiumSodium#e=2+8+1=#p#e=2+8+1=#p

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ChlorineChlorine#e=2+8+7=#p#e=2+8+7=#p

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Sodium ion Sodium ion #e=#p-1#e=#p-1

ChlorineChlorineion #e=#p+1ion #e=#p+1

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ElectronElectronCompletelyCompletelyTransferredTransferred

NegativeNegativechargecharge

PositivePositivechargecharge

Chapter 2 6ƒ2-3c

Ionic Bonding in NaClIonic Bonding in NaCl

ClCl-- ClCl-- ClCl-- ClCl--




NaNa++ NaNa++ NaNa++



NaNa++

NaNa++

NaNa++

NaNa++ NaNa++ NaNa++ NaNa++

Opposites attract.Opposites attract.

Sodiums nestle Sodiums nestle between between chlorines.chlorines.

Perfectly cubical Perfectly cubical crystals.crystals.








NaNa++

NaNa++

NaNa++

NaNa++ NaNa++ NaNa++ NaNa++

Chapter 2 7ƒ2-4c

Water Is CovalentWater Is Covalent

Electron pair forms Electron pair forms covalent bondcovalent bond

Each spends some Each spends some time w/one, then the time w/one, then the other atomother atom

Less time w/H, more Less time w/H, more time w/Otime w/O

Causes polarity of HCauses polarity of H22O O moleculemolecule

Chapter 2 8ƒ2-4cWater Molecule HWater Molecule H22OO

H HO

OxygenOxygen

HydrogensHydrogens

Chapter 2 9

Polar vs. Nonpolar BondsPolar vs. Nonpolar Bonds

Distribution of charge on moleculeDistribution of charge on molecule

Polar — charged surfacePolar — charged surface• Prefer other charged moleculesPrefer other charged molecules• Soluble in waterSoluble in water

Nonpolar — no residual chargeNonpolar — no residual charge• Prefer uncharged moleculesPrefer uncharged molecules• Soluble in oilsSoluble in oils

Chapter 2 10T2-3

BondingBondingPatterns of Common AtomsPatterns of Common Atoms

SulfurSulfur

PhosphorusPhosphorus

OxygenOxygen

NitrogenNitrogen

CarbonCarbon

HydrogenHydrogen

Chapter 2 11 Free RadicalsFree Radicals

Some cellular reactions produce free Some cellular reactions produce free radicalsradicals

• Free radicalFree radical: a molecule whose atoms have : a molecule whose atoms have one or more unpaired electrons in their outer one or more unpaired electrons in their outer shellsshells

Free radicals are highly unstable and Free radicals are highly unstable and reactivereactive

• Free radicals steal electrons, destroying other Free radicals steal electrons, destroying other moleculesmolecules

• Cell death can occur from free radical attackCell death can occur from free radical attack

Chapter 2 12 Free RadicalsFree Radicals

Free radicals are involved in causing Free radicals are involved in causing heart disease, Alzheimer’s, cancer, and heart disease, Alzheimer’s, cancer, and agingaging

AntioxidantsAntioxidants like vitamins C and E like vitamins C and E render free radicals harmlessrender free radicals harmless

13Chapter 2ƒ2-5

Hydrogen BondsHydrogen Bonds

OO

OO

HH

HH

HHHH++

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HydrogenHydrogenBondsBonds

Water molecules Water molecules carry slight carry slight chargescharges

Electrons favor Electrons favor OO over over HH

Water molecules Water molecules carry slight carry slight chargescharges

Electrons favor Electrons favor OO over over HH

Hydrogen bonds Hydrogen bonds form between form between OO of of one and one and HH of of anotheranother

Hydrogen bonds Hydrogen bonds form between form between OO of of one and one and HH of of anotheranother

Not a “REAL” Not a “REAL” bond!!! No bond!!! No transfer of transfer of electrons!electrons!

Not a “REAL” Not a “REAL” bond!!! No bond!!! No transfer of transfer of electrons!electrons!

Chapter 2 14 Hydrogen BondsHydrogen BondsHydrogen BondsHydrogen Bonds

Hydrogen bonds Hydrogen bonds are like two are like two children holding children holding very-slippery very-slippery hands.hands.

The bonds The bonds constantly break constantly break and reformand reform

Hydrogen bonds Hydrogen bonds are like two are like two children holding children holding very-slippery very-slippery hands.hands.

The bonds The bonds constantly break constantly break and reformand reform

Chapter 2 15ƒ2-6

NaCl Dissolved by WaterNaCl Dissolved by WaterNaCl is ionicly bonded

NaCl is ionicly bondedWater is polar and charged

Water is polar and chargedO sticks to Na+

O sticks to Na+

H sticks to Cl-

H sticks to Cl-

Chapter 2 162-7

DissociationDissociation

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WaterWaterWaterWater

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HydroxideHydroxideionion

HydroxideHydroxideionion

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HydrogenHydrogenionion

HydrogenHydrogenionion

A few water moleculesA few water moleculesnaturally naturally dissociatedissociate

A few water moleculesA few water moleculesnaturally naturally dissociatedissociate

• Hydroxide ionHydroxide ion is isnegative and negative and basicbasic

• Hydroxide ionHydroxide ion is isnegative and negative and basicbasic

• Hydrogen ionHydrogen ion is ispositive and positive and acidicacidic

• Hydrogen ionHydrogen ion is ispositive and positive and acidicacidic

Makes water a goodMakes water a goodsolventsolvent

Makes water a goodMakes water a goodsolventsolvent

HH22OOHydrogenHydrogen

BondBond

GlucoseGlucose

HH22OO

HH22OOHH22OOHH22OO

Chapter 2 17ƒ2-8

CohesionCohesionamong Water Moleculesamong Water Molecules

Chapter 2 18ƒ2-9

The pH ScaleThe pH Scale

NeutralNeutralpHpH++ = pOH = pOH––

Increasingly AcidicIncreasingly AcidicpHpH++ > pOH > pOH––

Increasingly BasicIncreasingly BasicpHpH++ < pOH < pOH––

0000 -1-1-1-1 -2-2-2-2 -3-3-3-3 -4-4-4-4 -5-5-5-5 -6-6-6-6 -7-7-7-7 -8-8-8-8 -9-9-9-9 -10-10-10-10 -11-11-11-11 -12-12-12-12 -13-13-13-13 -14-14-14-14

LemonLemonJuiceJuice

LimeLimeJuiceJuice

StomachStomachAcidAcid

CoffeeCoffeeUrineUrine

WaterWater

BloodBlood

SeaSeaWaterWater

BakingBakingSodaSoda

BleachBleach

AmmoniaAmmonia

OvenOvenCleanerCleaner

Chapter 2 19 Water Stabilizes TemperatureWater Stabilizes Temperature

Very low or very high temperatures may Very low or very high temperatures may damage enzymes or slow down damage enzymes or slow down important chemical reactionsimportant chemical reactions

Water moderates the effect of Water moderates the effect of temperature changetemperature change• Temperature reflects the speed of Temperature reflects the speed of

molecular motion molecular motion • It requires 1 calorie of energy to raise the It requires 1 calorie of energy to raise the

temperature of 1g of water 1temperature of 1g of water 1ooC (the C (the specific heatspecific heat of water), so it heats up very of water), so it heats up very slowlyslowly


Water requires a lot of energy to turn Water requires a lot of energy to turn from liquid into a gas (from liquid into a gas (heat of heat of vaporizationvaporization))• Evaporating water uses up heat from its Evaporating water uses up heat from its

surroundings, cooling the nearby surroundings, cooling the nearby environment (as occurs during sweating)environment (as occurs during sweating)

Because the human body is mostly water, Because the human body is mostly water, a sunbather can absorb a lot of heat a sunbather can absorb a lot of heat energy without sending her/his body energy without sending her/his body temperature soaringtemperature soaring

Chapter 2 21


Water requires a lot of energy to be Water requires a lot of energy to be withdrawn in order to freeze (withdrawn in order to freeze (heat of heat of fusionfusion))

Water freezes more slowly than other Water freezes more slowly than other liquidsliquids

Most substances become denser when Most substances become denser when they solidify from a liquidthey solidify from a liquid

Ice is unusual because it is Ice is unusual because it is less denseless dense than liquid waterthan liquid water

Chapter 2 23

Water molecules Water molecules spread apart spread apart slightly during the slightly during the freezing processfreezing process

Chapter 2 24

Chapter 2 25 Water Forms an Unusual SolidWater Forms an Unusual Solid

Ice floats in liquid waterIce floats in liquid waterPonds and lakes freeze from the top Ponds and lakes freeze from the top

down and never freeze completely to down and never freeze completely to the bottomthe bottom

• Many plants and fish therefore are not Many plants and fish therefore are not frozenfrozen

Chapter 2

The EndThe End

Technology

Ap Bio Ch2 PowerPoint