View
317
Download
0
Category
Preview:
Citation preview
Why Study Chemistry in Biology?
I. Atoms
Definition: smallest particle of an element
B. Composition
Subatomic Particle
Charge Mass Location
Proton +1 1 Nucleus
Neutron 0 1 Nucleus
Electron -1 1/1840 the mass of a
proton
Orbiting nucleus
C. If Neutral Atom: # protons = # electrons
II. ElementsA. Definition: substance that cannot be broken down into other substances
B. Biologically important elements i. Major: C H O N
ii. Minor: Ca Fe Mg I Se P K Na Cl
C. Symbol: usually from first letter or two of full name
Elements Con’t.
Atomic Mass 12.0107 amu
Mass Number
D. Atomic Number: # of protons in nucleus
ii. Atomic mass: count of the total number of protons and neutrons in an atom's nucleus
E. Atomic Mass / Mass Number
F. Isotopes
Mass Number
i. Definition: forms of the same element have same # of protons but different # of neutrons
ii. Radioactive isotopes: An isotope having an unstable nucleus that decomposes spontaneously
i. Molecules definition: two or more atoms held together by COVALENT bonds
G. Chemical Compounds
ii. Compound definition: a substance
containing two or more elements in a
fixed ratio– Ex: H2O, NaCl
Decoding Chemical Formulas??
C6H12O6
So in this molecule, there are 6 carbon atoms, 12 hydrogen, and 6 oxygen
Element subscript is the NUMBER of ATOMS
2H2O
• The number in front of H2O means
two entire molecules of H2O• Think of it like 2 x (H20)• Sooooo… how many total atoms of H are there?• Of oxygen?
• Atoms want to fill their outer energy
levels to be
• In order to do this, they will meet up with other atoms and either share or exchange electrons
• Atoms share electrons so that both atoms fill their outer energy level
A. Covalent Bonds
B. Ionic Bonds: gimme that electron!
• Atoms transfer electrons, becoming (+) or (-) charged
• This attraction brings them together– Ex: Na and Cl
i. Ions > An electrically charged atom
HydrogenHas 1 electron, needs 1 to fill its orbital
CarbonHas 4 electrons in outer level, needs 4 more to fill its orbital
Can form ONE bond
Can form FOUR bonds
IV. Water
A. Human Composition: 65–90% waterB. Plant Composition: 80-90%C. Formula: H2O
D. Bonds: i. Hydrogen bonds: the slightly (+) H atoms are attracted to nearby (-) O atoms, and develop a weak bond. ii. Covalent bonds: are shared between oxygen and hydrogen in a single molecule.
V. Water (con.’t)
5. Water is a polar molecule: i. Definition of polarity: molecule that has opposite electrical charges on opposite ends
ii. Why? Oxygen does not share electrons equally- pulls them closer to itself, making it more negative and Hydrogen more positive
V. Water (con.’t)
F. Unique molecule: i. Cohesion: 1. Definition: molecules of same kind stick to one another 2. Example: Surface tension; trees transporting water from roots to leaves
ii. Adhesion: 1. Definition: attraction that occurs between unlike molecules 2. Example: Water molecules and cotton string.
iii. Solutions: 1. Water is able to dissolve other polar and ionic compounds when mixed by causing the ions to break away and surround them.Ex.: Salt Water
2. Suspensions a. Definition: A heterogeneous mixture in which particles settle out of solvent-like phase some time after their introduction b. Example: oil & water
iv. Boiling Point: water will boil at 100C or 212F
G. Acids and Bases i. A water molecule can react to form ions ii. An ion is when a molecule breaks down and the atoms get a charge 1. Example: H+ and OH-
iii. pH Scale 1. How? Scale of 0-14; each pH unit represents a tenfold change in the concentration of H+ ions 2. Acid definition: pH 0-6 3. Base definition: pH 8-14
4. Buffer definition: substances that cause a solution to resist changes in pH.; works by accepting H+ ions when levels rise and donating H+ ions when levels fall, maintaining a constant pH a. Weak acid or base
Recommended