3.7 Particles and nuclear structure

Question 1

Define lepton

Answer 1

An elementary particle with low mass e.g electrons, neutrinos

Question 2

Define quark

Answer 2

An elementary particle not found in isolation which combines to form hadrons and baryons e.g. up, down

Question 3

Define hadron

Answer 3

A high mass particle consisting of quarks and/or anti-quarks

Question 4

Define baryon

Answer 4

A hadron composed of 3 quarks e.g. a proton or a neutron

Question 5

Define anti-baryon

Answer 5

A hadron composed of 3 anti-quarks e.g. an anti-proton

Question 6

What is the value of the elementary charge?

Answer 6

1.602 x 10^-19 C

Question 7

Define electron volt

Answer 7

The energy transfer when an electron moves through a potential difference of 1V

Question 8

Define and describe the 4 different interactions between particles, their effects, their range, and other points

Answer 8

• Gravitational: affects all matter, infinite range, negligible for subatomic particles
• Weak: affects all particles, range of approx 10^18m, only significant when EM and strong interactions are not involved
• EM: affects all charged particles, infinite range, also affects neutral hadrons as quarks have charges
• Strong: affects all quarks, range of approx 10^15m, also affects interactions between hadrons e.g. nuclear binding

Question 9

Describe in terms of forces how atoms are stable

Answer 9

• Electrons are bound to the nucleus by the EM force
• Protons and neutrons are held together in the nucleus by the strong force, which opposes the EM repulsion of the protons
• The weak force is responsible for the decay of neutrons in neutron rich nuclei, giving rise to beta- decay