Chemical Foundations

•Rattlebox moth

Nature’s Chemical Language

•Play many roles – Us– Other organisms– Physical environment

Nature’s Chemical Language

Elements

• Fundamental forms of matter

• Can’t be broken down further

• 92 occur naturally on Earth

• 25 are essential for life

Most Common Elements in Living Organisms

• Oxygen

• Hydrogen

• Carbon

• Nitrogen

Trace Elements

• Additives to food

• Dietary deficiencies

• Essential to health

What is an Atom?

• Smallest particle that is still an element

• Subatomic particles:– Protons (+)

– Electrons (-)

– Neutrons (no charge)

Hydrogen Helium

electron

proton

neutron

Examples of Atoms

Atomic Number

• # of protons• All atoms of an element the same• Atomic # H = 1• Atomic # C = 6

Mass Numbers

• Mass number (atomic mass)

= Number of protons + number of neutrons

• Carbon: 6 protons + 6 neutrons = 12

• Oxygen: 8 protons + 8 neutrons = 16

+

+

– –

+

–

2

2

2

Protons

Neutrons

Electrons

Massnumber = 4

+

+

2e–

Electroncloud

Nucleus

Isotopes

Different #s of neutrons

Radioisotopes

• Unstable nucleus • Emits energy and particles• Radioactive decay

– fixed rate

Uses of Radioisotopes

• Radiometric/carbon dating– Ratio of C 14 to C 12

• Tracers• Radiation therapy• Dangers

Uses of Radioisotopes

Will Atoms Interact?

Depends on:# and arrangement

of e-

Electron Shells• Shells hold e-• #s of shells

– Close = lower energy• filled 1st

Hydrogen (H)Atomic number = 1

Electron

Carbon (C)Atomic number = 6

Nitrogen (N)Atomic number = 7

Oxygen (O)Atomic number = 8

Outermost electron shell (can hold 8 electrons)

First electron shell (can hold 2 electrons)

Electron Vacancies

• Unfilled shells = likely rxn

• H, C, O, N– unfilled outer

shells

CARBON6p+ , 6e-

NITROGEN7p+ , 7e-

HYDROGEN1p+ , 1e-

Chemical Bonds, Molecules,

& Compounds• Bonds = electron interactions• Form molecules

• Compounds e.g.. - H2O

• Molecules e.g. - O2

Chemical Formulas

• Symbols

• Glucose is C6H12O6

– 6 carbons

– 12 hydrogens

– 6 oxygens

Chemical Formulas

• Chemical equation shows rxnReactants ---> Products

• Start and finish with = # of atoms

• HCL + NaOH NaCl + H2O

Important Types of Bonds

•Ionic Bonds (salt, NaCl)•Covalent Bonds (methane CH3)

•Hydrogen Bonds (water)

Ionic Bonding

• Atom loses e- -> (+) cation• Atom gains e- -> (-) anion• Difference charge?• Results?

Formation of NaCl

• Sodium atom (Na) – Outer shell e- ?

• Chlorine atom (Cl) – Outer shell e- ?

• Transfers e-

• Ions together as NaCl

Formation of NaClTransfer of electron

NaSodium atom

ClChlorine atom Na+

Sodium ion

Cl–

Chloride ion

Sodium chloride (NaCl)

Na Cl ClNa

+ ––

–

Na+

Cl–

Covalent Bonding

Atoms share e-

•Single covalent

bond

•Double covalent

bond

•Triple covalent bond

Molecular hydrogen

Polar or Nonpolar Bonds?

• Nonpolar: share electrons equally • Polar: unequal sharing

– Water – Will electrons spend more time with

the nucleus of O or H?

Hydrogen Bonding

• Polar covalent molecules

• Attraction to oppositely charged atom

Water molecule

Ammonia molecule

Figure 2.10

Water

• No net charge

• Oxygen has a slight ______ charge

• Hydrogen has a slight ______ charge

H H

O

Properties of Water

• Temperature stabilizing– Absorbs more heat

– Evaporation

– Forms crystal-lattice structure

– Wonders of ice!

Extra Photo 02.11x2

Properties of Water

• Cohesive – Due to hydrogen bonds

– Increases surface tension

– Vital property to many organisms

• Great solvent

Figure 2.12

Figure 2.16

Properties of Water

• Bonds to hydrophilic substances– Bonds to polar molecules

• Repels hydrophobic ones– Repels nonpolar molecules

Hydrogen Ions: H+

• Unbound protons

• Biological effects

• Form when water ionizes

The pH Scale

• Measures H+ concentration of fluid• Log scale (1 = 10X change)

Highest H+ Lowest H+

0---------------------7-------------------14Acidic Neutral Basic

Examples of pH

• Pure water pH of 7.0

• Acidic– Stomach acid: pH 1.0 - 3.0

– Lemon juice: pH 2.3

• Basic– Seawater: pH 7.8 - 8.3

– Baking soda: pH 9.0

Acids & Bases

• Acids

– Donate H+ when dissolved in water

– Acidic solutions have pH < 7

• Bases

– Accept H+ when dissolved in water

– Acidic solutions have pH > 7

Acid Deposition

Potential problem areasbecause of sensitive soils

Potential problem areas because of air pollution: emissions leading to acid depositionCurrent problem areas(including lakes and rivers)

Areas Affected and Threatened by Acid

Deposition

Extra Photo 02.18x2

Figure 2.18

Acid Rain

Extra Photo 02.18x1

Buffer Systems

• Minimize shifts in pH• Partnership between weak acid

and weak base

Blood pH

• Carbonic Acid-Bicarbonate Buffer System

• When blood pH rises, carbonic acid dissociates

to form bicarbonate and H+

H2C03 -----> HC03- + H+

• When blood pH drops, bicarbonate binds H+ to

form carbonic acid

HC03- + H+ -----> H2C03

Question of the Day

My new laundry detergent proudly

states “phosphate free”, why

should I be interested if my

detergent has phosphate? Should

I continue to buy this detergent?

Is it better? Safer?