Particle & Nuclear Physics Flashcards
How did Rutherfords alpha scattering experiment work?
- A narrow beam of alpha particles (all of the same kinetic energy) from a radioactive source was targeted at a thin piece of gold, only a few atoms thick
- The alpha particles were scattered by the foil and detected on a zinc sulfide screen mounted in front of a microscope
- Each alpha particles hitting the fluorescent screen produced a tiny speck of light
- The microscope was moved around in order to count the number of alpha particles scattered through different angles per minute, for 0 to almost 180 degrees
What were the observations of Rutherfords alpha scattering experiment?
- Most of the alpha particles passed straight through the thin gold foil with very little scattering
- Very few of the alpha particles (about 1 in 10,000) were defelected though angles of more than 10 degrees
What were the conclusions for Rutherfords alpha scattering experiment?
- Most of the atom was empty space, with most of the mass concentrated in a small region
- The nucleus has a positive charge because it repelled the few positive alpha charges that came near it
What is the charge of a proton?
1.6 x 10^-19 C
What is the charge of an electron?
- 1.6 x 10^-19 C
What is the charge of a neutron
0 C
What is the mass of a proton?
1.67 x 10^-27 kg
What is the mass of a neutron?
1.67 x 10^-27 kg
What is the mass of an electron?
9.11 x 10^-31 kg
What is the relative charge of a proton?
+1
What is the relative charge of a neutron?
0
What is the relative charge of a neutron?
-1
What is the relative mass of a proton?
1
What is the relative mass of a neutron?
1
What is the relative mass of an electron?
1/2000
What is the diameter of an atom?
1 x 10^-10 m
What is the diameter of a nucleus?
1 x 10^-15 m
What is the closest approach method?
- In the rutherford scattering experiment, alpha particles are fired at a thin gold foil
- Some of the alpha particles are found to come straight back from the gold foil
- This indicates that there is electrostatic repulsion between the alpha particles and the gold nucleus : KE = eV = 1/2 mv^2
- At the point of closest approach, r, the repulsive force reduces the speed of the alpha particles to 0 momentarily
- At this point : initial KE of alpha particle = electric potential energy
What is the closest approach equation?
KE = Qq / 4 pi ε r
What is the nucleon number?
Total number of protons & neutrons in the nucleus
What is the proton number?
Total number of protons in the nucleus
What is the notation showing nucleon and proton number of an element?
What is an isotope?
An atom (of the same element) that has an equal number of protons but a different number of neutrons. The proton number is the same but the nucleon number is different?
What can the nucleon number also be called?
Mass number