Chapter 2.4 The Observations that Led to the Nuclear Atom Model

Question 1

Cathode rays

Answer 1

Rays originating at the negative electrode (cathode) and moving to the positive electrode (anode)
cathode rays consist of negatively charged particls found in all matter

Question 2

Observations that established the properties of Cathode rays

Answer 2

1. Ray bends in magnetic field
2. Ray bends toward positive plate in electric field
3. Ray is identical for any cathode

Question 3

Conclusions that established the properties of Cathode rays

Answer 3

1. Consists of charged particles
2. Consists of negative particles
3. Particles found in all matter

Question 4

J.J Thomson (1897)

Answer 4

discovered atoms contain even smaller particles

Question 5

Robert Millikan (1908)

Answer 5

figured the minimum charge = charge of electron

Question 6

Electron’s charge

Answer 6

-1.602x10^19 C (C = Coulomb, SI unit for charge)

Question 7

Mass of electron

Answer 7

(Mass/Charge) x Charge = (-5.686x10^-12 kg/C)(-1.602x1-^-19C)

Question 8

Discovery of the Atomic Nucleus

Answer 8

1. Experimental design (Positively charged alpha particles are aimed at gold foil)
2. Expected results (only minor deflection of alpha particles)
3. Actual results (few alpha particles were deflected back)
4. Conclusion (an atom is mostly space occupied by electrons) & (in the center is a tiny region (nucleus) containing all the positive charge/mass of the atom (protons))

Question 9

James Chadwick (1932)

Answer 9

discovered the neutron