Atoms, Molecules and Water Essential Building Blocks for Living Organisms

Atoms, Molecules Atoms, Molecules and Water and Water

Essential Building Blocks Essential Building Blocks for Living Organismsfor Living Organisms

Comparison of Terms Comparison of Terms

ElementElement Substance that cannot be broken Substance that cannot be broken down to another substance with down to another substance with different propertiesdifferent properties

AtomAtom Smallest unit that has characteristic Smallest unit that has characteristic properties of the elementproperties of the element

MoleculeMolecule Two or more atoms joined by Two or more atoms joined by chemical bondschemical bonds

Composition Composition of an Atom of an Atom

• NucleusNucleus Proton = positively charged particle (+)Proton = positively charged particle (+) Neutron = uncharged particle (n or Neutron = uncharged particle (n or ++))Number of protons + Number of neutrons = Atomic massNumber of protons + Number of neutrons = Atomic massNumber of protons = Atomic numberNumber of protons = Atomic number • Electrons = negatively charged particlesElectrons = negatively charged particles

Number of electrons = Number of protons Number of electrons = Number of protons

Each electron circles the nucleus in an orbitEach electron circles the nucleus in an orbitrepresenting a specific energy level. representing a specific energy level.

CC121266

4Chapter 2ƒ2-1

Atomic ModelsAtomic Models

Hydrogen (H)Hydrogen (H) Helium (He)Helium (He)NucleusNucleus

ElectronElectronShellShell

5Chapter 2ƒ2-2

Different Kinds of AtomsDifferent Kinds of Atoms

HeliumHelium

Max 2eMax 2e--Max 2eMax 2e--

CarbonCarbon

+7p+7p++

+4p+4p++

+2p+2p++

InnermostInnermostelectron shellelectron shell

+4e+4e--

+4n+4n±±

+2n+2n±±

+2e+2e--

OxygenOxygenMax 8eMax 8e--Max 8eMax 8e--

+7e+7e--

+8n+8n±±

PhosphorusPhosphorus

+5p+5p++

+5e+5e--

+4n+4n±±

CalciumCalcium

22ee--

22nn 22pp++6e6e--

66nn 6p 6p++

8e8e--

88nn 8p 8p++15e15e--

1616nn 15p 15p++20e20e--

2020nn 20p 20p++

Applying Your Knowledge Applying Your Knowledge

MagnesiumMagnesium ChlorineChlorine

Atomic NumberAtomic Number 1212 1717

Atomic MassAtomic Mass 2424 3535

Number of ProtonsNumber of Protons

Number of NeutronsNumber of Neutrons

Number of ElectronsNumber of Electrons

Electron Energy LevelsElectron Energy Levels

Energy Energy LevelLevel

Capacity for Capacity for ElectronsElectrons

11 22

22 88

33 88

In forming molecules, atoms combine In forming molecules, atoms combine to fill their outer energy levels.to fill their outer energy levels.

Applying Your Knowledge Applying Your Knowledge

MagnesiumMagnesium ChlorineChlorine

Total Number of Total Number of Electrons Electrons

1212 1717

Number of Electrons Number of Electrons in First Electron Shellin First Electron Shell

Number Electrons in Number Electrons in Second Electron ShellSecond Electron Shell

Number of ElectronsNumber of Electrons

In Third Electron ShellIn Third Electron Shell

Chemical BondsChemical BondsForces holding atoms togetherForces holding atoms together

BondBond CharacteristicsCharacteristics

IonicIonic One atom loses an electron, One atom loses an electron, another gains an electronanother gains an electron

CovalentCovalent Atoms share electronsAtoms share electrons

Polar Polar CovalentCovalent

Atoms share electrons Atoms share electrons unequallyunequally

HydrogenHydrogen Covalently-bound hydrogen is Covalently-bound hydrogen is attracted to another atomattracted to another atom

±±++

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±±++±±++±±++ ±±++±±++±±

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±±++±±++±±++ ±±++±±++±±

++±±++

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Ionic Bonding in NaClIonic Bonding in NaCl

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±±++±±++±±++ ±±++±±++±±

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

±±++

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±±++±±++±±++ ±±++±±++±±

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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

––

ElectronElectronCompletelyCompletelyTransferredTransferred

NegativeNegativechargecharge

PositivePositivechargecharge

Ionic Bonding in NaClIonic Bonding in NaCl

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




NaNa++ NaNa++ NaNa++



NaNa++

NaNa++

NaNa++

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

• Opposites Opposites attract.attract.

• Sodiums nestle Sodiums nestle between between chlorines.chlorines.

• Perfectly Perfectly cubical crystals cubical crystals form.form.








NaNa++

NaNa++

NaNa++

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

Covalent BondingCovalent BondingOxygen AtomOxygen Atom Oxygen AtomOxygen Atom

Oxygen Molecule (O2)

In Water, Polar Covalent Bonds In Water, Polar Covalent Bonds Join Oxygen and Hydrogen Join Oxygen and Hydrogen

Hydrogen Bonds Join Water MoleculesHydrogen Bonds Join Water Molecules

OO

OO

HH

HH

HHHH+

+

+

–

–

+

+

HydrogenHydrogenBondsBonds

Water molecules Water molecules carry slight carry slight chargescharges

Electrons favor Electrons favor O over HO over H

Hydrogen bonds Hydrogen bonds form between O form between O of one water of one water molecule and H molecule and H of another of another

Due to hydrogen Due to hydrogen bonding, water showsbonding, water shows

Surface tension: concentration of Surface tension: concentration of hydrogen bonds at hydrogen bonds at air-water interface air-water interface

•Cohesion: water molecules associate Cohesion: water molecules associate with each otherwith each other


Capillary Action: movement of water Capillary Action: movement of water through a tube by through a tube by cohesion and adhesion cohesion and adhesion

Adhesion: water molecules associate Adhesion: water molecules associate with other molecules or surfaceswith other molecules or surfaces


Imbibition: movement of water into wood Imbibition: movement of water into wood or gelatin by capillary action or gelatin by capillary action

Due to hydrogen bonding, Due to hydrogen bonding, water resists temperature changewater resists temperature change

Water has high values forWater has high values for

Specific Heat: heat needed Specific Heat: heat needed to change temperatureto change temperature

Heat of Vaporization: heat needed to Heat of Vaporization: heat needed to convert liquid to gas convert liquid to gas

Due to hydrogen bonding, Due to hydrogen bonding, density decreases upon freezingdensity decreases upon freezing

Ice floats!Ice floats!

Water as a SolventWater as a Solvent

• Substances that dissolve in water = Substances that dissolve in water = hydrophilichydrophilic– PolarPolar– IonicIonic

• Substances that are insoluble in Substances that are insoluble in water = hydrophobicwater = hydrophobic– Non-polar Non-polar

NaCl Dissolves in WaterNaCl Dissolves in Water

Ionic bonds Ionic bonds of NaCl give of NaCl give +/- charges +/- charges

Water has Water has partial +/- partial +/- chargescharges

O tends O tends to join to join with Nawith Na++

H tends H tends to join to join with Clwith Cl--

DissociationDissociation

++

WaterWaterWaterWater

––

HydroxideHydroxideionion

HydroxideHydroxideionion

++

HydrogenHydrogenionion

HydrogenHydrogenionion

A few water molecules naturally A few water molecules naturally dissociatedissociate into ions into ions

A few water molecules naturally A few water molecules naturally dissociatedissociate into ions into ions

• Hydroxide ionHydroxide ion is negative and is negative and basicbasic• Hydroxide ionHydroxide ion is negative and is negative and basicbasic

• Hydrogen ionHydrogen ion is positive and is positive and acidicacidic• Hydrogen ionHydrogen ion is positive and is positive and acidicacidic

The pH ScaleThe pH Scale

NeutralNeutralpHpH++ = pOH = pOH––

Increasingly AcidicIncreasingly AcidicpHpH++ > pOH > pOH––

Increasingly BasicIncreasingly BasicpHpH++ < pOH < pOH––

0000 1111 2222 3333 4444 5555 6666 7777 8888 9999 10101010 11111111 12121212 13131313 14141414

LemonLemonJuiceJuice

LimeLimeJuiceJuice

StomachStomachAcidAcid

BeerBeerCoffeeCoffee

UrineUrine

WaterWater

BloodBlood

SeaSeaWaterWater

BakingBakingSodaSoda

BleachBleach

AmmoniaAmmonia

OvenOvenCleanerCleaner

101000101000 1010-1-11010-1-1 1010-2-21010-2-2 1010-3-31010-3-3 1010-4-41010-4-4 1010-5-51010-5-5 1010-6-61010-6-6 1010-7-71010-7-7 1010-8-81010-8-8 1010-9-91010-9-9 1010-10-101010-10-10 1010-11-111010-11-11 1010-12-121010-12-12 1010-13-131010-13-13 1010-14-141010-14-14

1010-14-141010-14-14 1010-13-131010-13-13 1010-12-121010-12-12 1010-11-111010-11-11 1010-10-101010-10-10 1010-9-91010-9-9 1010-8-81010-8-8 1010-7-71010-7-7 1010-6-61010-6-6 1010-5-51010-5-5 1010-4-41010-4-4 1010-3-31010-3-3 1010-2-21010-2-2 1010-1-11010-1-1 101000101000

Applying Your KnowledgeApplying Your Knowledge

• What would be the chemical formula if What would be the chemical formula if magnesium and chlorine united to form magnesium and chlorine united to form a molecule? a molecule? (Mg=magnesium; Cl=chlorine) (Mg=magnesium; Cl=chlorine)

• Which electrons from each atom are Which electrons from each atom are involved in forming the bond(s)?involved in forming the bond(s)?

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Atoms, Molecules and Water Essential Building Blocks for Living Organisms