History+of+the+Atomic+Model--Unit+2

(1) Who first thought of the idea of the atom? How was his idea accepted?

(2) Describe the postulates of Dalton’s understanding of the atom. Daltons atomic theory rests on the following postulates: all matter consists of tiny particles, atoms are indestructable and unchangeable, elements are characterized by the mass of their atoms, and when elements react, their atoms combine in simple, whole-number ratios. Mandy Yost ﻿He thought of it as small particles that just helped shaped everything he reaaly didnt know a whole lot about it he just thought about that it was the what made elements. Jesse Hill (Be sure you are familiar with the postulates that Mandy describes--Mrs. K.) (3) What did Henri Becquerel discover? How did it happen? He discovered, phosphorescent minerals emitted Xrays in more basic terns, spontaneous radioactivity. It happened accidentally. but specifically, he found out that uranium salts causes fogging of an unexposed photographic plate. -Reba Cox (That is right, Reba. He discovered radioactivity when he put some uranium in a drawer that had photographic film. The film was exposed, even though it had not been exposed to light--Mrs. K.) (4) What did J.J. Thomson discover? Briefly describe how he did this.

(5) What was J.J. Thomson’s model of the atom called? Describe it. J.J. Thomson’s model was called the plum pudding model. The model consisted of a spherically shaped atom composed of a uniformly distributed positive charge in which the individual negatively charged electrons resided. Cynthia Funk (Good job Cynthia--Mrs. K.) (6) What did Millikan find out about the electron? Briefly describe his experiment.

(7) Describe Rutherford’s gold foil experiment.

(8) What significant information was learned from Rutherford’s gold foil experiment? His "gold foil experiment" led to the discovery that most of an atom's mass is located in a dense region now called the nucleus. Hailey Stevens (That's right Hailey--he realized that atoms were mostly empty space with a small dense positively charged center--Mrs. K.)

Rutherford's experiment discovered that even though most of the alpha particles passed straight through the gold foil, some of them were deflected off at large angles. He found that most of the mass is concentrated in the nucleus and the electrons take up the most space. The reason that some of the alpha particles were deflected was because they hit the nucleus. Sam Long (Sam, this is right--you really described some of his experiment, which is good since no one else did--Mrs. K.)

(9) Describe Bohr’s model of the atom. Bohr's picture model shows the atom as a small positively charged nucleus that is surrounded by electrons. Those electrons travel in circular orbits around the nucleus. (Who are you? You are right--Bohr thought that electrons orbit the nucleus like planets around the sun. We now know that they do not have set paths like planets do--Mrs. K.) (10) What particle did Chadwick discover? Why was this particle more difficult to identify? James Chadwick discovered the subatomic neutral particle called the neutron. This particle was more difficult to identify because the neutron's lack of total electric charge makes it difficult to steer or accelerate them,unlike charged particles which can be accelerated, decelerated, deflected by electric or magnetic fields. - LaKedra White (Great answer LeKedra--Mrs. K.) (11) What is our current understanding of the structure of the atom? The **atom** is a basic unit of matter that consists of a central nucleus surrounded by negatively charged electrons. The atom's nucleus contains positively charged protons and neutral neutrons - Barron Stuckey (Good job Barron--Mrs. K.)