Chapter 4 Notes (4)

Sections 4-1,4-2

I.Development of an Atomic Model

*Matter:

anything that has mass and volume

 *Indirect Evidence:

evidence you get without actually seeing or touching the object

-Greek Model (Democritus)*atom:

smallest particle of an element that has the prop of the element

~atomos: meaning not to be cut

-Dalton’s Atomic Theory1. All elements are composed of

atoms2. Atoms of the same element are

exactly alike

3. Atoms of diff. elements are diff.

4. Compounds are formed by joining of atoms of 2 or more elements

II. A Divisible Atom

-Thomson’s Model:

~Plum Pudding

*Electrons: - charge

-Rutherford’s Model~Gold Foil Experiment ~the atom was mostly empty space with a dense, positively charged nucleus in the center.

*Nucleus: the center of the atom

-Bohr Model

~electrons move in definite orbits around the nucleus

 

-Wave Model (Today accepted model)~electrons don’t move about in a definite path~probable location is based on how much nrg the electron has

• SEE HISTORY OF THE ATOM WEBSITE

• http://hi.fi.tripod.com/timeline/

III. Subatomic Particles 

*smaller than the atom

-Three main subatomic part.1.     proton2.     neutron3.     electron **quarks (make up 1 & 2)**

-Nucleus

*center of the atom

mass (amu) charge location

~proton: 1 + nucleus

~neutron: 1 +/- nucleus

~electron: 1/1836- e- cloud

*Atomic Mass Unit (amu):

measures mass of subatomic part.

 

-?? Where does it come from??

-Atomic #

*number of + in the nucl

~identifies the element

~never chngs

 

-Isotopes

*same # of +, but diff # of neutrons

  EX:

-Mass # and Atomic Mass

*sum of the + and neutrons in its nucleus

*Aver Atomic mass:

aver of the masses of all the atoms in the sample.

~mass # - atomic# = #of neutrons

 

III. stop

3 H Nuclear Notation1

Hydrogen-3 Hyphenated Notation

III. continue

-Electrons (e-)*e- cloud:

place in which e-’s are likely to be found

~location depends upon how much nrg the e- has

*nrg levels: most likely location of the e-

  ~2,8,8.*Valence e-:

e- outer most nrg level

~Movement of e-’s:

-in: lose nrg

-out: gain nrg

IV. Forces Within the Atom

Video #14

-The four forces that account for the behavior of sub part

1.     electromagnetic force*either attract or repel particles

video #15

2.     strong force

*opposes electromag force of repulsion between +

~only when + are very close together

3.     weak force*key to the power of the sun~responsible for radioactive

decay~ +/- ---> + and -

4.     gravity*weakest force known in nature~force of attraction exerted

between all objects