B. Composition Subatomic Particle ChargeMassLocation Proton+11Nucleus Neutron01Nucleus Electron1/1840 the mass of a proton Orbiting nucleus C. If Neutral Atom: # protons = # electrons
II. Elements A.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: H 2 O, NaCl
Decoding Chemical Formulas?? C 6 H 12 O 6 So in this molecule, there are 6 carbon atoms, 12 hydrogen, and 6 oxygen Elementsubscript is the NUMBER of ATOMS
2H 2 O The number in front of H 2 O means two entire molecules of H 2 O Think of it like 2 x (H 2 0) 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
IV. Water A.Human Composition: 65–90% water B.Plant Composition: 80-90% C.Formula: H 2 O 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