Ch24 particle physics

Question 1

alpha scattering experiment

Answer 1

fire alpha particles from a source at a gold sheet.

-most/majority went through, suggesting that most of the nucleus is empty space.
-some of the alpha particles got deflected at a small angle, suggesting that the nucleus has the same charge as the alpha particle ( positive charge)
-few of the alpha particles got deflected at a big angle, suggesting that the mass of the nucleus is concentrated at the centre.

Question 2

nuclear model of the atom

Answer 2

A = nucleon number
Z = proton number
X= chemical symbol of the element

so neutron number:
= A (nucleon number) - Z (proton number)

Question 3

estimating the size of the nucleus.

Answer 3

all of the initial KE of the alpha particle gets converted to electric potential energy.
KE = PE
KE = PE equation.
rearrange r in the equation and sub-values to work out the size of the nucleus.

Question 4

atomic mass unit.u.

Answer 4

u = 1.661x10^-27kg

Question 5

R = ro x A

Answer 5

R= ro x A
R = radius
ro = constant
A = nucleon number

Question 6

density of the nucleus

Answer 6

P=m/v
v = 4/3πR^3
sub in R = ro x A in the equation to work out the density of the nucleus.

Question 7

fundamental forces.

Answer 7

• gravitational force, acts between particles that have mass ( protons and neutrons).
  -electrostatic force, acts between particles that have charge (protons).
  -strong nuclear force, acts between all particles.
  -weak nuclear force, responsible for beta decay.

Question 8

strong nuclear force.

Answer 8

-acts on all particles in the nucleus (nucleons)
-short ranged force (fms)
-repulsive force between 0 and 0.5fm
-attractive between 0.5 and 3.0fm
-beyond 3.0fm it tends toward zero.

Question 9

fundamental particle

Answer 9

every particle has a corresponding anti-particle with that same mass but opposite charge.
electron corresponds to positron
same mass of 9.11x10^-31

Question 10

hardons and leptons.

Answer 10

hardons and particles are made up of quarks and are affected by the strong nuclear force.
e.g. protons and nuetrons.
leptons are fundamental particles that are not affected by the strong nuclear force.
e.g. electrons, positron, muons.
both hardons and leptons are affected by the weak nuclear force.

Question 11

quarks and anti-quarks

Answer 11

up = 2/3e
down = -1/3e
strange = -1/3e
anti-up = -2/3e
anti-down = 1/3e
anti-strange = 1/3e

Question 12

beta decay

Answer 12

weak nuclear force is responsible for beta decay

beta plus decay:
protons => neutron + positron + nutrino
u => d + positron + nutrino

beta minus decay:
neutron => proton + electron + anti-nutrino
d => u + electron + anti-nutrino