2. Composition of the Nucleus

Question 1

What is β-decay?

Answer 1

-a nuclear process resulting in the emission of an electron

Question 2

Showing that there can be no electrons in the nucleus

Answer 2

-follows from the uncertainty principle
-assume that the electron’s momentum p is at least the uncertainty in its momentum Δp:
p > Δp > h/Δx = 6.63x10^(20) kgm/s
-where Δx, uncertainty in position, is taken as the nuclear radius, 10^(-14)
-finding E using
E = √(p²c² + m²c^4)
= 124MeV
-but β decay electrons generally have energies of the order 1MeV, this discrepancy shows that they must be created at the moment of decay

Question 3

Discovery of the Proton

Answer 3

-when nitrogen is bombarded with α particles, it can undergo the following reaction:
α + (14,7)N -> (17,8)O + (1,1)H
-this confirmed suspicions that larger nuclei contain the nucleus of hydrogen, i.e. a proton

Question 4

Discovery of the Neutron

Answer 4

-bombarding beryllium with α particles produces neutral articles with mass very similar to the proton, i.e. the neutron

Question 5

Modern Understanding of the Atom

Answer 5

-electrons ‘orbit’ a nucleus consisting of protons and neutrons, which are bound together by their mutual attraction through the strong nuclear force