The Chemistry of Life: Atoms and Molecules

Periodic Table 112 known elements Pure substances that cannot be broken down into simpler chemical entities by ordinary chemical reactions. Periodic Table 112 known elements

Major Elements Comprising the Biological Molecules of Living Things Carbon Hydrogen Oxygen Nitrogen Phosphorus Sulfur

Elements & Atoms An element is composed of atoms (0.1-1 nm in diameter) Atom cluster of small particles (proton, neutron, electron)

Subatomic Particles Protons (p +) Neutrons (n o) Electrons (e -)

Electron Shell Configurations of Atoms proton neutron electron hydrogen atom helium atom carbon atom 1p, 0n, 1e- 2p, 2n, 2e- 6p, 6n, 6e-

atomic number: number of p; #p = #e- 2He2e- and 2p

atomic mass (atomic wt.): sum of masses of p+n He 2p + 2n, atomic mass = 4 4 2He He p + n e-

Carbon Atom C p = n = e- = Atomic number = Atomic mass =

Isotope C atoms that differ in the number of neutrons 12 6 C 13 6 C 14 6 C C12 C13 C14 stable stable isotope unstable- radioactive isotope

Two or more atoms held together by chemical bonds Molecule Two or more atoms held together by chemical bonds Oxygen O2 Nitrogen N2 Ammonia NH3 Carbon Dioxide CO2 Water H2O Methane CH4 Glucose C6H12O6

Compound Binding two or more different kinds of elements together NaCl + C6H12O6

Compound Binding two or more different kinds of elements together NaCl CH4 C6H12O6

Ion An atom that has either gained or lost electrons such that it exhibits a net charge Na+ Cl-

Sodium (Na) Atom 11 P+ 12 No

Sodium (Na+) Ion + 11 P+ 12 No

Chlorine (Cl) Atom 17 P+ 18 No

Chloride (Cl-) Ion _ 17 P+ 18 No

Some Examples of Ions Hydrogen H+ Potassium K+ Fluoride F- Calcium Ca+2 Magnesium Mg+2

Complex Ions Hydroxide OH- Bicarbonate HCO3- Nitrate NO3- Phosphate PO4-3 Ammonium NH4+ Acetate C2H3O2-

Bond Types: Ionic Covalent Hydrogen

Ionic Bonds Transfer of electron 11 P+ 12 No 17 P+ 18 No

Covalent Bonding: electron sharing

Covalent Bonding: electron sharing

Hydrogen Bonding Between Water Molecules Covalent bond

Hydrogen Bonding Between Different Molecules

Examples of Organic Molecules Lipids Carbohydrates Proteins Nucleic acids

Properties of Water High heat capacity-absorbs and releases large amounts of heat (land heats faster than water) High heat of vaporization- sweat, cooling mechanism Polarity solvent properties- universal solvent Reactivity- hydrolysis and condensation (dehydration)

Polarity of Water Molecules

Chemical Reactions A  B reactant  product

Chemical Synthesis A + B  AB

Chemical Decomposition AB  A + B

Chemical Rearrangement AB + CD  AC + BD

Decomposition of Water H2O  OH- + H+ O O + H H H H Water molecule [H2O] Hydroxyl ion [HO-] Hydrogen ion [H+]

pH “p” stands for potential and “H” stands for hydrogen Refers to the potential of a substance to attract hydrogen ions (H+)

Acids HCl  H+ + Cl- Proton donor, i.e., they donate H+ ions HCl is a strong acid with a pH 1-2 HCl  H+ + Cl-

Bases Na+ + OH-  NaOH NH3 + H+  NH4 OH - + H+  H2O HCO3 +H+  H2CO3 Proton acceptor, i.e., they take up H+ ions NaOH is a strong base ~pH 12 Na+ + OH-  NaOH NH3 + H+  NH4 OH - + H+  H2O HCO3 +H+  H2CO3

Neutralization HCl + NaOH H2O + NaCl

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

pH Scale Type of Solution pH Value Neutral 7 Acidic 0-6 0-14 Type of Solution pH Value Neutral 7 Acidic 0-6 Basic (alkaline) 8-14

pH Scale Logarithmic scale blood

Measuring pH

pH of Coke

Impact of Acid in our Body - CO2 + H2O H2CO3 HCO 3 + H+ O2 Bicarbonate Carbonic acid Capillary Cell CO2 O2

Impact of Acid in our Body HCl pH 1-2

Impact of Acid in our Body pH 8

Impact of Acid in the Ocean

Inquiry How many neutrons in 7 N? 14 Of the following pH’s which is most acidic? 3 7 6 2 3. 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 14