Nuclear

Question 1

2 observations + deductions of Rutherford α particle scattering experiment

Answer 1

Observations

1. Most of the α-particles pass through undeflected through gold film
   deduction: nucleus very small in size & atom largely made out of empty space
2. Very few (1/8000) α-particles deflected by large scattering angles (>90deg) or are deflected directly backwards
   deduction: almost all the mass of the atom is concentrated in the centre of the atom (nucleus)
   => nucleus is highly dense in mass & +ve charged

Question 2

Amount of deflection 4 factors

Answer 2

1. Impact parameter
2. Mass & initial velocity of projectile
3. Charge of target
4. Charge of projectile

Question 3

Definition: Nucleus

Answer 3

dense region at the centre of an atom containing protons & neutrons

Question 4

Nuclear force origins

Answer 4

Within nucleus, protons packed together in tiny space=> strong repulsive force
=> even stronger attractive force required to **bind protons & neutrons together*

Same between proton & proton / proton & neutron / neutron and neutron
Extremely short range, acts over 1-3fm, not beyond closest nucleon

Question 5

Definition: Isotopes + properties

Answer 5

Atoms of the same element with same proton no. but different neutron no.

• Similar _chemical properties_ => inseparable via chemical means
• Different _nuclear & physical properties_ => different mass - separate via mass spectrometer

Question 6

Definition: Nuclides

Answer 6

Atomic species with specific mass no.(A) & proton no.(Z)

Question 7

Definition: Unified atomic mass constant (u)

Answer 7

One atomic mass unit (1u) is equal to 1/12 mass of carbon-12 atom

Question 8

Definition: Mass defect

Answer 8

Difference between total mass of nucleons of atom taken separately & mass of nucleus

Mass defect= [Z x M_p + (A-Z) x M_n] - M_nucleus

Note: Mass of nucleus < total mass of individual nucleons