Class Notes 9/182007

15 min discuss homework

15-20 min lichen lab, microscope use

30 min chemistry lecuture

Chemistry Overview (Campbell Chapter 2)

Last week

Elements

All matter is made up of basic elements. An element is the simplest form of a substance that cannont be broken down any further by ordinary chemical means (analagous to cell). Elements are groups according to their properties. This grouping is represented by the periodic table. 92 elements occur naturally and other have been synthesized in the lab. Examples include carbon, hydrogen and oxygen. About 25 of 92 elements are known to be essential to life, but 4 C, O, N, H make up 96% of living matter. More on biological molecules next week.

Compounds

Elements combine to form coumpounds in specific proportions and has different properities than the elements that combined for form is. H, O, H2O. Na, Cl, NaCL.

Molecules

The smallest part of a substance that still has the properties of that substance is a molecule.

Atoms, basic units of matter, building blocks of everything

protons, positively charged particle located in the nucleus

electrons, negatively charged particle that orbits around the nucleus

neutrons netral partcle loacted in the nucles

subatomic particles, what you get with particle accelerator, not important for now

nucleus, center of atom, where protons and neutrons are located

Atoms are the building blocks of all matter.

Atomic number (number of protons, defines and element)

Atomic mass (number of proton + number of neutrons)

energy levels

Isotopes elements that have the same atomic number but different atomic masses due to different number of neutrons

Carbon usually has 6 neutrons for an atomic mass of 12, but sometimes has 8 neutrons for an atomic mass of 14. Carbon 14 used to carbon dating. Carbon 14 decays to carbon 12. Ration of C12 to C14 can tell age. Atomic mass of carbon is a weighted average of isotopes 12.011. Carbon 12 much more common. There is also C13. C12 and C13 are stable. C14 has a half life of 5600 years.

Chemical Reactions

Energy Levels

Chemical Bonds

interations between electrons

The chemical behavior of an atom is determined by its electron configuration, specifically the electrons in its outermost shell. Atoms with the same number of electrons in their outer shell exhibit similar properties. Noble gasses-unreactive, halides

onic bonds: electron transfer, salts

covalent bonds: sharing of electrons, polar vs. non polar

hydrogen bionds: intramolecular, weaker, water, uniqueness of water

Chemical reactions take place when chemical bonds are formed and broken

activation energy

spontaneous reaction

endothermic net absorb energy

exothermic, net give off energy

pH Scale

A measure of the hydrogen ion H+ concentration.

Biological functions usually take place in a very narrow pH range.

Logrithmic scale

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