1.2-STABLE AND UNSTABLE NUCLEI Flashcards
What does a stable isotope have?
nuclei that does not disintegrate, so there must be a force holding them together
What is the force holding the protons + neutrons together in the nuclei called?
strong nuclear force
What force does the strong nuclear force balance out?
It overcomes the electrostatic force of repulsion between the protons in the nucleus and keeps the protons and neutrons together
What is the range of the strong nuclear force?
no more than about 3-4 femtometres (fm)
What do 1 fm equal to in m?
1 fm = 10^(-15)m
What is the range of the strong nuclear force about the same as?
diameter of a small nucleus
What is the range of the electrostatic force between two charged particles like?
has an infinite range (although it decreases as the range increases)
How does the strong nuclear force effect protons and neutrons?
it has the same effect between two protons as it does between two neutrons or a proton and neutron
From what range is the strong nuclear force an attractive for?
from 3-4 fm down to about 0.5 fm
What happens to the strong nuclear force when the separation is smaller than 3-4 fm to 0.5fm?
it is repulsive force that acts to prevent neutrons and protons being pushed into each other
What do naturally occurring radioactive isotopes release?
3 different types of radiation:
alpha, beta, gamma
Which force has the larger range?
electrimagetic
What does alpha radiation consist of?
alpha particles which each comprise two protons and neutrons
What is the proton number and mass number of an alpha particle?
proton number - 2
mass number - 4
What happens to the numbers of an unstable nucleus of an element X when it emits an alpha particle?
its nucleon number decreases by 4 and its atomic number decreases by 2
What happens as a result of the alpha particle being emitted? (element)
the product nucleus belongs to a different element Y
How do you detect alpha radiation?
Tracks left by alpha alpha particles are seen in a cloud chamber.
Geiger counter of spark counters detect the ionising radiation - see the count rate drop if you slowly move it away from the source.
What does beta radiation consist of?
fast-moving electrons with electron antineutrino’s
What is the charge and mass of a beta particle like?
its charge is equal and opposite to that of the proton
its mass is much smaller than the proton’s mass
Why does an unstable nucleus of an element X emit a beta particle?
Nucleus is isotope is neutron rich.
The neutron in the nucleus changes into a proton.
What else is emitted with the beta particle?
an antiparticle with no charge, called an antineutrino
What happens in Beta radiation?
What numbers increase / stay the same?
One of the neutrons from the nucleus is changed into a proton. The beta particle is created and is emitted instantly
Proton number increases by 1, Nucleon number stays the same
Antineutrino particle is released
What does the antineutrino carry?
Some energy and momentum
What do neutrinos have / not have and why?
Needed to conserve energy
Neutral charge, zero / almost zero mass, carries momentum and energy
