1/22 p2 Atomic Theory Notes

1. 1/22 p2 Atomic Theory Notes IQ: Which statement below best describes Charles Darwin’s theory of natural selection and Alfred Wegener’s theory of continental drift? A. The theories answer all scientific questions about evolution and continental drift. B. The development of their theories was influenced by many scientists. C. Planned experiments were used to develop these theories. D. These theories are an example of how scientific theories do not change over time.

2. ATOMSWhat are they, & how do we know they’re there?!

3. Atoms • Basic unit of matter • The smallest particle of a substance that has all of its properties. • Called the ‘building blocks’ of matter • Example= the elementGold is made of gold atoms; all exactly the same, IF gold!!

4. Atomic Timeline AKA: The 7 Dead Dudes of Atomic Theory

5. 1) Democritus - 460 BC • Firstto develop the idea that matter was made of particles called atoms. • Atoms in different materials were of different shapes/sizes which led to different properties. Ex. Pepper atoms were spiky. • The term “Atoms” comes from the Greek word “atomos” which means “indivisible”

6. 2) John Dalton - 1803 • Performed experiments with different substances. Dalton’s work, Atoms and molecules i. Proposed atoms combine in specific proportions to make new stuff. ii. An atom is indivisible, indestructible, tiny sphere iii. Atoms of the same element are exactly alike. iv. Determined that elements have unique atomic masses.

7. 3) Joseph John Thomson - 1898 • Discovered electrons through the use of a cathode ray tube, proved that atomswere further divisible. • Mass of e-s 1800 times lighter than hydrogen atom (lightest known). • Cathode Ray tube animation Proposed an atomic model known as the “plum pudding” model (electrons = raisins in plum pudding; scattered throughout) or chocolate chip ice cream.

8. OQ: Describe 2 ways that John Dalton’s work was different from Democritus’s.

9. 1/23 Atomic Theory cont’d • IQ: True or False? • Democritus believed that different atoms combined to form new stuff. • Dalton stated that atoms of all elements were exactly alikewith equal masses. • JJ Thomson proved that atoms were divisible.

10. 4) Ernest Rutherford - 1911 • Performed the Gold Foil experiment, and discovered positively charged nucleus by with positively charged particles called protons. • Gold foil experiment step by step • Gold Foil Experiment animation • Proposed atomic model with massive (small but heavy) nucleus with electrons in a circle around it in a solar system model

11. 5) Niels Bohr - 1913 • Developed atomic model that placed electrons in specific energylevels or orbits to explain why they did not spiral toward & collide with the nucleus. • E-s can jump between levels by gaining or losing energy as light. • Model animation • Bohr model • Atomic models

12. OQ: Which particles (with charges) were discovered by Rutherford- ________ protons Thomson- _______ ________

13. 1/24 P6 Atomic Theory Notes cont’d IQ: Whose model is represented above? • Democritus • Dalton • JJ Thomson • Rutherford

14. 6) James Chadwick - 1932 • Discovered neutron as a neutral particle in the nucleus with the same mass as a proton (+). • The discovery explained why the mass of an atom could not be attributed entirely to the mass of the p+s. • Neutrons keep the protons/nucleus together with a “strong force.” • Discovery of neutrons. (+) Positive Protons (0) Neutral Neutrons Nucleus (protons & neutrons)

15. 7) Erwin Schrodinger – 1926 • Described electrons as waves with their probable location viewed as a cloudand introduced a mathematical model of the atom. Most current model. • Impossible to locate an e-’s exact position. • Cloud model e-

16. Brainpop • Timeline

17. Highlights

18. OQ:In order to jump farther away from the nucleus, an electron will need toa. lose energyb. gain energyc. gain more charged. lose some charge