The Chemistry of Life: The Chemistry of Life: Atoms and Molecules Atoms and Molecules

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Pure substances that cannot be broken down into simpler chemical entities by ordinary chemical reactions.

Pure substances that cannot be broken down into simpler chemical entities by ordinary chemical reactions.

ElementsElements

Periodic Table 112 known elements

Major Elements Comprising Major Elements Comprising the Biological Molecules of the Biological Molecules of

Living ThingsLiving Things

Major Elements Comprising Major Elements Comprising the Biological Molecules of the Biological Molecules of

Living ThingsLiving Things

• CCarbonarbon• HHydrogenydrogen• OOxygenxygen• NNitrogenitrogen• PPhosphorushosphorus• SSulfurulfur

Other Major Elements of Living Things

Other Major Elements of Living Things

• Calcium (Ca)Calcium (Ca)• Potassium (K)Potassium (K)• Chlorine (Cl)Chlorine (Cl)• Magnesium (Mg)Magnesium (Mg)

Some Important Trace Some Important Trace Elements of Living ThingsElements of Living Things

Some Important Trace Some Important Trace Elements of Living ThingsElements of Living Things

• Boron (B)Boron (B)• Cobalt (Co)Cobalt (Co)• Iron (Fe)Iron (Fe)• Copper (Cu)Copper (Cu)• Fluorine (F)Fluorine (F)• Zinc (Zn)Zinc (Zn)

An element is composed of atoms (0.1-1 nm in diameter)

Atom cluster of small particles (proton, neutron, electron)

Elements & AtomsElements & Atoms

Subatomic ParticlesSubatomic ParticlesSubatomic ParticlesSubatomic Particles

Protons (p +)

Neutrons (n o)

Electrons (e -)

Electron Shell Configurations of AtomsElectron Shell Configurations of Atoms

proton

neutron

electron

hydrogenatom

heliumatom

carbonatom

1p, 0n, 1e- 2p, 2n, 2e- 6p, 6n, 6e-

atomic number: number of p; #p = #e-

2He2e- and 2p

He

atomic mass (atomic wt.): sum of masses of p+nHe 2p + 2n, atomic mass = 4

4

2He

He

p + n e-

p = n = e- = Atomic number = Atomic mass =

C

Carbon Atom

C12 C13 C14stable stable isotope unstable- radioactive isotope

IsotopeIsotopeatoms that differ in the number of neutrons

12

6 C13

6 C14

6 C

C

MoleculeMoleculeTwo or more atoms held

together by chemical bondsOxygenOxygen OO2 2

NitrogenNitrogen NN22

AmmoniaAmmonia NHNH33

Carbon DioxideCarbon Dioxide COCO22

WaterWater HH22OO

MethaneMethane CHCH44

GlucoseGlucose CC66HH1212OO66

CompoundCompoundBinding two or more different kinds of elements together

NaClNaCl

CHCH44

CC66HH1212OO66

IonIon

An atom that has either gained or lost electrons

such that it exhibits a net charge

Na+

Cl-

Sodium (Na) Sodium (Na) AtomAtom

11 P+

12 No

Sodium (NaSodium (Na++) Ion) Ion

11 P+

12 No

+

Chlorine (Cl) Chlorine (Cl) AtomAtom

17 P+

18 No

Chloride (ClChloride (Cl--) Ion) Ion

17 P+

18 No

_

Some Examples of IonsSome Examples of Ions

HydrogenHydrogen HH++

PotassiumPotassium KK++

FluorideFluoride FF--

CalciumCalcium CaCa+2+2

MagnesiumMagnesium MgMg+2+2

HydroxideHydroxide OHOH--

BicarbonateBicarbonate HCOHCO33--

NitrateNitrate NONO33--

PhosphatePhosphate POPO44-3-3

AmmoniumAmmonium NHNH44++

Acetate CAcetate C22HH33OO22--

Complex IonsComplex Ions

Bond TypesBond Types:• Ionic• Covalent• Hydrogen

Ionic BondsIonic BondsTransfer of electron

17 P+

18 No

11 P+

12 No

Covalent Bonding:Covalent Bonding: electron sharing

O

HH

Covalent Bonding:Covalent Bonding: electron sharing

C

H

H

H

H

C

H

H

H

H

Hydrogen Bonding Hydrogen Bonding Between Water MoleculesBetween Water Molecules

Covalent bond

Hydrogen bond

Hydrogen Bonding Between Hydrogen Bonding Between Different MoleculesDifferent Molecules

Examples of Organic Examples of Organic MoleculesMolecules

Properties of WaterProperties of Water

1. High heat capacity-absorbs and releases large amounts of heat (land heats faster than water)

2. High heat of vaporization- sweat, cooling mechanism

3. Polarity solvent properties- universal solvent

4. Reactivity- hydrolysis and condensation (dehydration)

Polarity of Water Polarity of Water MoleculesMolecules

Chemical ReactionsChemical Reactions

A BA B

reactant reactant product product

Chemical SynthesisChemical Synthesis

AA ++ BB AABB

Chemical Chemical DecompositionDecomposition

AABB AA ++ BB

Chemical Chemical RearrangementRearrangement

AABB ++ CCDD AACC ++ BBDD

HH22OO OOHH- - ++ HH++

OOHH H

H+

Water molecule[H2O]

Hydroxyl ion[HO-]

Hydrogen ion[H+]

Decomposition of Decomposition of WaterWater

AcidsAcids

HCL H+ + Cl-

Proton donor, i.e., they donate H+ ions

HCl is a strong acid with a pH 1-2

BasesBases

Na+ + OH- NaOHNH3 + H+ NH4

OH - + H+ H2O

HCO3 +H+ H2CO3

Proton acceptor, i.e., they take up H+ ions

NaOH is a strong base ~pH 12

NeutralizationHCl + NaOH H2O + NaCl

Buffer- resists dramatic changes in pH; ex. tums, rolaids…buffers stomach acid

pH ScalepH Scale

Neutral 7Acidic 0-6Basic (alkaline) 8-14

Type of Solution pH Value

0-14

Logarithmic scale

pH ScalepH Scale

Inquiry

1. How many neutrons in 7 N?2. Of the following pH’s which is most

acidic? 3 7 6 23. The symbols K, Na, C, and S are:4. Which of the following are elements?water; sugar; table salt; the atmosphere

5. Which of the following are pure substances?

wine; seawater; blood; iron

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