Ap CHemistryAp CHemistryChapter TwoChapter Two

Atoms & ElementsAtoms & Elements

Please do not memorize dates--I will never ask you for an exact one.However, you should have an idea (century-wise) of when

events/discoveries happened.

Ben FranklinBen Franklin1706-1790Two types charge

Positive & negative

Charges balance

If there is a positive charge,

somewhere there is a negative charge of equal magnitude

Still didn’t know about electrons

But had electricity

Henri BecquerelHenri Becquerel 1852-1908 1852-1908

Uranium on photographic plates

Emitted Rays

Pals with Marie Curie

She called it radioactivity

Marie Curie

Isolated polonium and radium

Cathode Ray TubeJ. J. Thompson

Evacuated glass tube

Metal electrodes

electric current produced glowing beamBent by magnetic field

ElectronsPlease to go the following link:

http://www.youtube.com/watch?v=IdTxGJjA4Jw

There are more slides

Ernest Rutherford

Nucleus small, dense

Gold Foil Experiment1909

Positive charge

Atom mostly empty space

Please go to this web page, but there are more slides after this one

http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/ruther14.swf

Robert Milliken1868-1953

Measured charge on electronOil Drop Experiment

http://video.google.com/videosearch?hl=en&q=oil%20drop%20experiment&ie=UTF-8&sa=N&tab=iv#

Please follow this link

Like a perfume sprayer

Gives droplets a charge

James Chadwick 1891- 1974Neutron

Alpha particles hit beryllium

Beryllium released radiation

Radiation hit wax & caused protons to come off

Atomic Number & Mass

Cr24

51.99

Z= atomic numberalso = #protons

Atomic number gives atom its identity

Average massfrom isotopes

Mass from neutrons and protons

Relative mass

Look at atom’s mass in relation to the mass of carbon

The Mole

Latin: heap

1 mole = 6.022 x 1023

Li6.941

1 mole = 6.022 x 1023 atoms, ions, molecules

3Al13

26.98This many grams = 1 moleDifferent for each element

But

AlwaysDiatomic

H, N,O , and HalidesNeed to double massN

14.0 1 mole = 28.0 g

The Periodic LawMendeleevarranged by mass

Moseley

arranged by atomic masscurrently

http://videos.howstuffworks.com/hsw/5810-atomic-structure-periodic-law-video.htm

Please view the following 2 links

http://videos.howstuffworks.com/hsw/5811-atomic-structure-modern-periodic-table-video.htm

http://www.youtube.com/watch?v=JrK8mK_v1XY

Quiz yourselfQuiz yourselfExperimented with photographic plates& discovered radioactivityHenri Becquerel

Named Becquerel’s discovery radioactivityMarie Curie

Who discovered the electron & what experimentJ.J. Thompson, Cathode Ray

How did Thompson determine the electron was negativeBent in magnetic field

What scientist demonstrated the existence of the nucleus & what experiment

Rutherford, Gold foil

What else did Rutherford’s experiment show about the nucleussmall, dense, + charge, contributes the mass

Who measured the charge on the electron & what experimentMillikan, Oil drop

What is the atomic number of oxygen,how many electrons & protons8,8,8What is the mass of 1 mole of oxygen32.0 g It is diatomic

The mass of the elements are relative to what other element Carbon

What elements are diatomichydrogen, nitrogen, oxygen and the halidesWho is credited with the first periodic table &

how was it arranged?Mendeleev, by mass

Who changed Mendeleev’s arrangement, and how are the elements currently ordered?Moseley, by atomic number

100 %!!!