Name___________________________________Date_______________________Period____
3.1 The History of the Atom – Atomic Theory Video Quest
Applied
Objectives:• Compare and contrast the developing theories of the model throughout history. • Summarize the five essential points of Dalton’s atomic theory.
• Explain the relationship between Dalton’s atomic theory and the laws of conservation of mass, definite proportions, and multiple proportions.
• Summarize the observed properties of the cathode rays that led to the discovery of the electron. • Summarize the experiment carried out by Rutherford and his coworkers that led to the discovery of
the nucleus.
• List the properties of protons, neutrons, and electrons. • Define the atom.
• Define the atomic number and mass number. Background:
The atom is one of science’s greatest achievements. The idea, born in the mind of a Greek man thousands of years ago, now dominates the science and technology that surrounds us. With this idea scientists can explain nearly all the phenomena of nature. With this idea technicians have developed TV, radio, computers; they’ve probed the human body and mind, and the farthest reaches of outer space.
Directions:
Below you will find the names of several individuals throughout scientific history who have helped to advance the model of the atom. Using the video links given below, which are also posted under the “3.1 History of the Atom Video Quest” folder on eBackpack, provide responses to the following questions and/or statements.
Be sure to provide yourself with thorough and detailed responses as these will serve as your notes for this section.
The Timeline of the Atomic Theory
Video Link: “History of the Atom (Atomic Theory)” - The Science Classroom
https://www.youtube.com/watch?v=IO9WS_HNmyg&index=2&list=PLfWuBca_SOr_fViaErg wQP18HRZ82AJe7
Democritus (460-370 B.C.)
1) ________________________ was the first person to come up with the idea of an atom. He actually used the word ___________________, which is a Greek word for uncutable or smallest indivisible particle.
2) There were really two main parts to Democritus’s theory. Atoms are
_____________________ and they are also ______________________. Aristotle (470-370 B.C.)
1) At the same time Democritus lived, there was another popular idea to what matter was made of. This idea was proposed by __________________________.
2) Aristotle did not believe that matter was made up of tiny particles called atoms, but rather that matter was made up of five basic elements. List these five basic elements below.
a. ______________________ b. ______________________ c. ______________________ d. ______________________ e. ______________________ John Dalton (1808)
1) It wasn’t until the early 1800’s that a man named _________________________ developed the atomic theory that would be based on his experimental evidence and observations.
2) Dalton’s theory has 5 main postulates. List these five postulates of Dalton’s Atomic Theory below. a. _______________________________________________________________ _______________________________________________________________ b. _______________________________________________________________ _______________________________________________________________ c. _______________________________________________________________ _______________________________________________________________ d. _______________________________________________________________ _______________________________________________________________ e. _______________________________________________________________ _______________________________________________________________ J.J. Thomson (1897)
1) Dalton’s idea that atoms are indivisible was held to be true for almost the next 100 years until the work of ___________________________.
2) Thomson discovered that the atom could be ___________________ and he discovered a negatively charged part of the atom called the ___________________.
3) JJ Thomson worked with a device called the ___________________________________. This device was a sealed glass container that has two electrodes separated by a vacuum. When a voltage was applied across these electrodes, _____________________________ were created. In other words, a stream of ______________________ that would move across the glass tube. When the particles struck the other end of the tube, a glowing patch was created, thus visualizing where the particles were.
4) Thomson discovered that if he used a magnetic field, he was able to move or deflect these particles. Thomson found that these particles would always move towards the
______________________ charge. He was thus able to conclude that these particles were ________________________ charged.
5) Thomson revised the atomic theory to include these particles. He called his theory the ______________________________ model. It is kind of like a chocolate chip cookie, where the chocolate chips represent the electrons, which are embedded in the rest of the atom. The rest of the atom would be represented by the rest of the cookie.
Ernest Rutherford (1911)
1) _______________________________ is responsible for the discovery of a positively charged particle of the atom that’s called the _____________________.
2) Rutherford fired alpha particles at a very thin sheet of _______________ foil. Alpha particles are relatively massive particles and they were travelling at such high speeds, so Rutherford and his colleagues expected the particles to be able to pass right through the gold foil. This though, was not the case. To Rutherford’s surprise, he found that some of the particles scattered and some even deflected almost right backwards.
3) Rutherford and his colleagues believed that there must be a very massive particle directly in the _________________ of the atom and this particle must be __________________ charged. They also believed that the electrons, rather than being embedded within the atom, were actually circling around the outside of this central particle. And so that atom was mostly _________________ space.
James Chadwick (1932)
1) ________________________ was responsible for the discovery of the ________________________.
2) We now know that the neutrons are located in the _____________________ of an atom along with the protons.
3.1 The History of the Atom – Atomic Theory Video Quest – Evaluation Quiz
Directions: Using your “History of the Atom – Atomic Theory Video Quest” notes, provide answers to the following questions/statements.
____1. Which of the following key points describes Democritus’s theory of the atom? a. Atoms are indivisible
b. Both a. and c.
c. Atoms are indestructible
____2. Who disagreed with the views of Democritus and said that all matter was composed of five basic elements; earth, water, air, fire, and aether?
a. John Dalton b. Aristotle
c. Werner Heisenberg
____3. Which of the following was NOT one of the 5 main postulates described in Dalton’s atomic theory?
a. All matter is composed of atoms.
b. Atoms cannot be created nor destroyed.
c. Each individual atom of an element has its own unique properties and behaviors. ____4. What is the name of the scientists who developed the “Plum Pudding” model of the atom?
a. Ernest Rutherford b. John Dalton c. J.J. Thomson
____5. What is J.J. Thomson credited with discovering? a. The positively charged electron
b. The negatively charged electron c. The negatively charged neutron
____6. Which scientist is credited with discovering the neutrally charged neutron located in the nucleus of an atom?
a. Ernest Marsden b. James Chadwick c. Neils Bohr
____7. What are the two main conclusions of Rutherford’s Experiment? a. The atom is mostly empty space.
b. The electron is negatively charged.
c. The atom has a dense positively charged center (nucleus). d. Matter is composed of earth, wind, water, fire, and aether e. Both a. and c.
f. Both b. and d.
____8. Which term best describes the “smallest indivisible particle”? a. Atomos
b. Plum Pudding Model c. Alpha Radiation
