Chapter 4 Flashcards
0
Q
John Dalton
A
- English Chemist
- Developed an atomic theory which used scientific method
- Elements are made of invisible particles called atoms (not invisible=not true)
- Atoms of the same element are identical. Atoms from 1 element= dif from other element
- Atoms from diff atoms form mixtures/ compounds
- Chem. reactions arrange atoms in dif combos, but atoms can’t change from one atom to another.
1
Q
Democritus’ Atomic Theory
A
- Greek Philosopher
- Suggested the existence of atoms
- Believed atoms were indivisible and indestructible
- Theory flawed cuz: didn’t explain chem. behavior
- Not based scientific method
- Not supported by experiment data
2
Q
How did John Dalton observe atoms?
A
- Observed when atoms mix, they maintain their own identity unless they combine in a chem. reaction
- Studied ration of these combinations
3
Q
Evidence from Daltons experiments
A
-Every drop of mercury has the same chemical properties
4
Q
J.J. Thomson
A
- Stated electrons are negatively charged particles
- Proved by filling with gas and put electrodes at each end connected to source of electricity
- Neg electrode: cathode
- Positive electrode: anode
- When electricity passed through tube, stream of light appears (cathode ray)
5
Q
Explanation of J.J. Thomson’s experiment
A
- Anode attracts cathode ray
- Cathode repels the cathode ray
- Cathode ray=stream of tiny neg charged particles (fast moving)
- Names particles corpuscles (electrons)
- type of gas in tube does not effect electrons
6
Q
Robert A Millikan
A
- Carried out experiment to measure an electrons charge
- Oil-droplet experiment: suspended neg charged oil droplets between two charged plates
- Changed the voltage on the plates to see how this affected the droplet’s fall
7
Q
Robert A Millikan charge of electron
A
-Found the charge of each oil droplet to be a multiple of 1.6 x 10^-19 coulomb ( the charge of an electron)
8
Q
Eugen Goldstein
A
- Observed the cathode ray tube: found rays traveling in the opposite direction of the cathode rays
- concluded rays were subatomic positive particles (protons)
9
Q
James Chadwick
A
-Confirmed the existence of the neutrons
10
Q
Plum Pudding Model
A
-JJ Thomson thought electrons were evenly distributed throughout a postitively charged atoms
11
Q
Plum pudding model vs. Atomic Model
A
- PP no nucleus
- PP spread through out the atom
- PP Protons have no definite shape and appear as dough in a ball of cookie dough
- PP no neutrons
- PP no empty space
- PP no motion
12
Q
Rutherford’s Gold Foil experiment
A
- Shot alpha beams (Helium atom wo/ electrons) through gold foil
- If plum pudding model was correct, beams would pass through (atoms are soft)
- What happened: most passed through, some went in diff direction
- Concluded: Existence of Nucleus, nucleus is dense w/ positive charge, most of atom is empty space
13
Q
Rutherford’s atomic model
A
- Protons and neutrons located in positive charged center(nucleus)
- electron orbits the nucleus
- Nucleus as small as marble in football stadium
14
Q
Atomic number
A
- Number of protons in element
