Chemical Foundations
Nature’s Chemical Language • Rattlebox moth
Nature’s Chemical Language • Play many roles – Us – Other organisms – Physical environment
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)
Examples of Atoms electron proton neutron Hydrogen Helium
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 e– Electron cloud + + Nucleus 2 + Neutrons 2 2 Protons – Electrons Mass number = 4
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 1 st Outermost electron shell (can hold 8 electrons) First electron shell (can hold 2 electrons) Electron Hydrogen (H) Atomic number = 1 Carbon (C) Atomic number = 6 Nitrogen (N) Atomic number = 7 Oxygen (O) Atomic number = 8
Electron Vacancies • Unfilled shells = likely rxn • H, C, O, N – unfilled outer shells CARBON 6 p+ , 6 e- NITROGEN 7 p+ , 7 e- HYDROGEN 1 p+ , 1 e-
Chemical Bonds, Molecules, & Compounds • • Bonds = electron interactions Form molecules Compounds e. g. . - H 2 O Molecules e. g. - O 2
Chemical Formulas • Symbols • Glucose is C 6 H 12 O 6 – 6 carbons – 12 hydrogens – 6 oxygens
Chemical Formulas • Chemical equation shows rxn Reactants ---> Products • Start and finish with = # of atoms • HCL + Na. OH Na. Cl + H 2 O
Important Types of Bonds • Ionic Bonds (salt, Na. Cl) • Covalent Bonds (methane CH 3) • Hydrogen Bonds (water)
Ionic Bonding • • Atom loses e- -> (+) cation Atom gains e- -> (-) anion Difference charge? Results?
Formation of Na. Cl • Sodium atom (Na) – Outer shell e- ? • Chlorine atom (Cl) – Outer shell e- ? • Transfers e • Ions together as Na. Cl
Formation of Na. Cl – – + Transfer of electron Na Na Sodium atom Cl Chlorine atom – Cl Na+ Sodium ion Cl– Chloride ion Sodium chloride (Na. Cl) 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 O H H
Properties of Water • Temperature stabilizing – Absorbs more heat – Evaporation – Forms crystal-lattice structure – Wonders of ice!
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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 p. H Scale • Measures H+ concentration of fluid • Log scale (1 = 10 X change) Highest H+ Lowest H+ 0 -----------7 ----------14 Acidic Neutral Basic
Examples of p. H • Pure water p. H of 7. 0 • Acidic – Stomach acid: p. H 1. 0 - 3. 0 – Lemon juice: p. H 2. 3 • Basic – Seawater: p. H 7. 8 - 8. 3 – Baking soda: p. H 9. 0
Acids & Bases • Acids – Donate H+ when dissolved in water – Acidic solutions have p. H < 7 • Bases – Accept H+ when dissolved in water – Acidic solutions have p. H > 7
Acid Deposition
Areas Affected and Threatened by Acid Deposition Potential problem areas because of sensitive soils Potential problem areas because of air pollution: emissions leading to acid deposition Current problem areas (including lakes and rivers)
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Figure 2. 18
Acid Rain
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Buffer Systems • Minimize shifts in p. H • Partnership between weak acid and weak base
Blood p. H • Carbonic Acid-Bicarbonate Buffer System • When blood p. H rises, carbonic acid dissociates to form bicarbonate and H+ H 2 C 03 -----> HC 03 - + H+ • When blood p. H drops, bicarbonate binds H+ to form carbonic acid HC 03 - + H+ -----> H 2 C 03
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?
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