1/20 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.

ATOMS What are they, & how do we know they’re there?! Under the IQ, draw what you think an atom looks like inside a penny. Think about its shape, relative size, and does it have any smaller parts/pieces inside.

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 element Gold is made of gold atoms; all exactly the same, IF gold!!

Atomic Timeline AKA: The 7 Dead Dudes of Atomic Theory

1) Democritus BC First to 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”indivisible

2) John Dalton Performed experiments with different substances. Dalton’s work, Atoms and molecules Dalton’s workAtoms 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. Review 2mins Review 2mins

OQ: Describe 2 ways that John Dalton’s work/theory was different from Democritus’s, 1 way it was similar.

1/21 Atomic Theory cont’d IQ: True or False? 1.Democritus believed that different atoms combined to form new stuff. 2.Dalton stated that atoms of all elements were exactly alike with equal masses. 3.Dalton believed that atoms could not be further divided. 4.Democritus and Dalton both proposed that atoms are tiny spheres.

3) Joseph John Thomson Discovered electrons through the use of a cathode ray tube, proved that atoms were 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.

4) Ernest Rutherford Performed the Gold Foil experiment, and discovered positively charged nucleus with positively charged particles called protons. Gold foil experiment step by step Gold foil experiment 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

OQ: Rutherford discovered ________ly charged protons located in the _________, whereas Thomson discovered- _______ charged ________ located in a positive cloud.

1/22 P6 Atomic Theory Notes cont’d IQ: Whose model is represented above? Provide evidence to support your answer. a.Democritus b.Dalton c.JJ Thomson d.Rutherford

5) Niels Bohr Developed atomic model that placed electrons in specific energy levels 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

6) James Chadwick 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)

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

Brainpop Timeline How Protons, electrons and neutrons were discovered (Youtube) How Protons, electrons and neutrons were discovered

Highlights 1. DemocritusFirst - Atomos - Indivisible 2. John DaltonAtomic Thoery - Add Together 3. J.J. ThomsonElectrons - “Plum Pudding” 4. Ernest Rutherford+ Charged Nucleus - Gold Foil 5. Niels BohrElectrons Specific NRG Levels 6. James ChadwickNeutrons (Jimmy Neutron) 7. Erwin SchrodingerElectron Cloud Wave

OQ: In order to jump farther away from the nucleus, an electron will need to a. lose energy b. gain energy c. gain more charge d. lose some charge