1.2-STABLE AND UNSTABLE NUCLEI

Question 1

What does a stable isotope have?

Answer 1

nuclei that does not disintegrate, so there must be a force holding them together

Question 2

What is the force holding the protons + neutrons together in the nuclei called?

Answer 2

strong nuclear force

Question 3

Why is the strong nuclear force called the ‘strong nuclear force’?

Answer 3

because it overcomes the electrostatic force of repulsion between the protons in the nucleus and keeps the protons and neutrons together

Question 4

What is the range of the strong nuclear force?

Answer 4

no more than about 3-4 femtometres (fm)

Question 5

What do 1 fm equal to in m?

Answer 5

1 fm = 10^(-15)m

Question 6

What is the range of the strong nuclear force about the same as?

Answer 6

diameter of a small nucleus

Question 7

What is the range of the electrostatic force between two charged particles like?

Answer 7

has an infinite range (although it decreases as the range increases)

Question 8

How does the strong nuclear force effect protons and neutrons?

Answer 8

it has the same effect between two protons as it does between two neutrons or a proton and neutron

Question 9

From what range is the strong nuclear force an attractive for?

Answer 9

from 3-4 fm down to about 0.5 fm

Question 10

What happens to the strong nuclear force when the separation is smaller than 3-4 fm to 0.5fm?

Answer 10

it is repulsive force that acts to prevent neutrons and protons being pushed into each other

Question 11

What do naturally occurring radioactive isotopes release?

Answer 11

3 different types of radiation:

alpha, beta, gamma

Question 12

What does alpha radiation consist of?

Answer 12

alpha particles which each comprise two protons and neutrons

Question 13

What is the proton number and mass number of an alpha particle?

Answer 13

proton number - 2

mass number - 4

Question 14

What happens to an unstable nucleus of an element X when it emits an alpha particle?

Answer 14

its nucleon number decreases by 4 and its atomic number decreases by 2

Question 15

What happens as a result of the alpha particle being emitted? (element)

Answer 15

the product nucleus belongs to a different element Y

Question 16

What does beta radiation consist of?

Answer 16

fast-moving electrons

Question 17

What is the charge and mass of a beta particle like?

Answer 17

its charge is equal and opposite to that of the proton

its mass is much smaller than the proton’s mass

Question 18

Why does an unstable nucleus of an element X emit a beta particle?

Answer 18

this happens as a result of a neutron in the nucleus changing into a proton. the beta particle is created and is emitted instantly

Question 19

What else is emitted with the beta particle?

Answer 19

an antiparticle with no charge, called an antineutrino

Question 20

How does the beta particle being emitted affect the element X?

Answer 20

atomic number decreases by 1 but the nucleon number stays the same

Question 21

What happens to the product nucleus after beta particle being emitted?

Answer 21

belongs to a different element Y

Question 22

What type of nuclei undergo beta decay?

Answer 22

nuclei that have too many neutrons

Question 23

What is gamma radiation?

Answer 23

electromagnetic radiation emitted by an unstable nucleus

Question 24

What can gamma radiation pass through?

Answer 24

thick metal plates

Question 25

What is the charge and mass like of gamma radiation?

Answer 25

no mass and no charge

Question 26

What type of nucleus emits gamma radiation and what is it followed by?

Answer 26

emitted by a nucleus with too much energy, following an alpha or beta emission

Question 27

What was found when the energy spectrum of beta particles was first measured?

Answer 27

beta particles were released with kinetic energy up to a maximum that depended on the isotope

Question 28

What did scientists think happened after they found out beta particles were released with K.E. up to a maximum that depends on the isotope ?

Answer 28

either energy was not conserved in the change or some of it was carried away by mystery particles

Question 29

What were the mystery particles called that carried some charge away?

Answer 29

neutrinos and antineutrinos

Question 30

How were antineutrinos detected over 20 years later?

Answer 30

as a result of their interaction with cadmium nuclei in a large tank of water

Question 31

Where was the large tank of water where antineutrinos were discovered installed?

Answer 31

next to a nuclear reactor as a controllable source of these very elusive particles