history of the Atom: those annoying people plus the forces at work on atoms

Question 0

Dalton

Answer 0

(1803) proposing the Atomic Theory:
* all elements are made of atoms that cannot be created or destroyed
* atoms of the same element are exactly alike
* atoms of different elements are different(different properties+mass)
* compounds are formed by the joining together atoms of of 2+ elements

Question 1

Democritus

Answer 1

“Hey, you know, I don’t think that we can actually split matter down into smaller and smaller pieces. I think that somewhere along the line, we have to reach the smallest piece.”

Question 2

Thomson

Answer 2

(1897) “Oh, look! The atom is composed of smaller pieces! Shoot, does that mean that we need to change the name now? Hmmm- oh, Contemporary! I figured out that atoms are made of smaller particles!”
Contemporary: “What?”
Him: “I took my cathode ray tube-“
Contemporary: “What’s that?”
Him: “It is a tube. With a positively charged top, and negatively charged bottom-“
Contemporary: “But, like, gas is neutral!”
Him: “It’s made of of positive-negative pairs!”
Contemporary: “I don’t understand you, Jesus/Lord-like Capital H ‘Him’.”
Him: “Think of plum pudding, where the pudding is positive, and the plums are negative.”
Contemporary: “Now I’m hungry. C’mon.”

Question 3

Rutherford

Answer 3

(1909) “let’s shoot some negatively charged alpha particles at a thin sheet of gold paper surrounded by a detector ring! Actually, no. I’m going to have you all, my glorious students, do it. Then you’ll be the ones who get really bad eyesight. Or at least die from radiation.
Student: “whatever you say, boss. But why?”
Him: “oh, I have absolutely no reason to suspect that anything will happen, other than prove the plum pudding model, but do it anyway. And I can say that because you are my cheap labor graduate student!.”
Student(muttering):” well this will be fun.”
later——
Student:”Teacher! Teacher! You wouldn’t believe what just happened! One in every 8000 particles bounces back, and only a few are deflected! Most go straight through!”
Him:”funny, i thought that most all of them would be deflected. Huh. Well, I guess that means that there is a center, the nucleus, with a positive charge, a lot of empty space, and negative particles scattered around.”
Student:”Genius teacher!”

Question 4

Niels Bohr

Answer 4

1913- “well, I don’t think the universe is so scattered. I bet that there are orbital paths, and each little path has its own energy level, with higher energy paths farther from the nucleus. Plus, how cool would it be if the electrons could JUMP from place to place?

Question 5

James Chadwick

Answer 5

(1932) discovered the neutron. “I am a big, strong, gorilla bear! I will use brute force to BOMBARD beryllium foil with more of those negatively charged alpha particles! And the masses- a neutron must weigh about as much as a proton.”

Question 6

Present Day Model of the Atom

Answer 6

Wave Model- based on wave mechanics

• positively charged nucleus, with neutrons and protons
• electrons in a cloud around the nucleus
• location and speed of an electron can’t be know simultaneously, tough location can be approximated by energy level- higher the farther from the nucleus,

Question 7

Gravity

Answer 7

Depends on mass and distance; masses are so small, it doesn’t really matter

Question 8

Electromagnetic

Answer 8

Force between charged particles; holds electrons around the nucleus- like charges repel, opposite charges attract

Question 9

Strong Force

Answer 9

Greater than electromagnetic force, but acts over very short distances- keeps protons together in the nucleus

Question 10

Weak

Answer 10

Important in radioactive atoms with an unstable nucleus-helps emit particles/energy to get to a more stable state