atomic history & atomic structure!

Atomic History & Atomic Structure!• Notebook Add-ons:– P. 22: Unit 1 Test– P. 23: “Unit 2 Key Terms”– P. 24: “Unit 2 Proficiency Tracker”– P. 25: “Atomic Theory Timeline” Chart– P. 26: Periodic Table– P. 27: Title: “Notes: Atomic Structure– P. 28: “Atomic Structure Chart”

• Homework!– Finish “Atomic Structure Chart”– Study for Quiz!!!– Start working on your Project! (Due 9/30)

Mystery Box

• With your table group… try to figure out what is inside the “Mystery Box”

• DON’T OPEN IT!!!!

• How small is an atom???• http://www.youtube.com/watch?v=aQnbF-zp

DiM

Atomic Theory

• Discuss with your table groups your research findings on your scientist.

Atomic Theory Timeline

Fill in your chart!

John Dalton (1803)

Dalton’s Postulates

1) All elements are composed of tiny indivisible particles called atoms.

2) Atoms of the same element are identical. The atoms of any one element are different from those of any other elements.

3) Atoms of different elements can physically mix together or can chemically combine with one another in simple whole-number ratios to form compounds.

4) Chemical reactions occur when atoms are separated, joined, or rearranged. Atoms of one element, however, are never changed into atoms of another element as a result of a chemical reaction.

Dalton’s Postulates

• We now know that certain parts of this theory are invalid.

• Part 1 – False. Atoms have been split.• Part 2 – Partially False. Some atoms of the

same element have more neutrons. (However, atoms of different elements are different.)

• Part 3 – True!• Part 4 – True!

Dalton’s Model

• Just a tiny ball with no parts inside

J. J. Thomson (1897)

J. J. Thomson• Used a cathode ray tube to shoot an electrical

charge through it.• Saw that the particles were deflected towards

the positive end of the tube.– This must mean that atoms contained a NEGATIVE

charge!• Discovered the ELECTRON.

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

http://www.youtube.com/watch?v=RW_zfKOU9uM

Thomson’s Model

• “Plum Pudding” or “Chocolate Chip Cookie Dough” Model.

• A ball of positive charge containing a number of electrons.

Ernest Rutherford (1911)

Ernest Rutherford

• Did the Gold Foil Experiment– Shot alpha (positively charged)

particles at a sheet of gold foil.• Saw that most particles passed

through the foil and some deflected straight back at different angles.

• Means that atoms are mostly empty space but contain a densely packed positive center….– Discovered the NUCLEUS

http://www.youtube.com/watch?v=wzALbzTdnc8&NR=1

http://www.youtube.com/watch?v=5pZj0u_XMbc

Rutherford Model

Nucleus

Empty Space

Electrons

Dense, positively charged nucleus

Surrounded by electrons (mostly empty space)

Niels Bohr (1913)

Niels Bohr

• Electrons travel in definite orbits around the nucleus

• Electrons are found in “energy levels”• AKA Planetary Model

http://www.youtube.com/watch?v=wCCz20JOXXk

Bohr Model

Nucleus

Electrons(orbiting the

nucleus)

Atomic Structure

p. 27

Proton

Neutron

Electron

particle Symbol Relative Mass

Charge Location

Proton p+ 1 +1 Nucleus

Electron e- 0 -1 Electron cloud

Neutron n0 1 0 Nucleus

Element Info on the Periodic Table

Element Name

Atomic Number (#protons)

Element Symbol

Atomic Mass

Other Info

• Mass Number = #p + #n• NOT the same as Atomic Mass… you

CAN’T find this on the P.T.!• # of electrons: – If #of electrons is the same as the # of

protons --- NEUTRAL ATOM– If the # of electrons is NOT the same as

the # of protons --- ION

Beans activity

• A Carbon atom has:– 6 protons– 6 neutrons– 8 electrons

• Create a “bean atom” of carbon.

Atomic Symbols

6C12 2-

Mass Number (#protons + #neutrons)

Charge (#protons - #electrons)

Atomic Number (#protons)