SP4c Radioactive Decay

Question 1

State 3 facts about stable nuclei.

Answer 1

.a stable nuclaus does not change over time
.smaller atoms that are stable have approximately the same number of protons as neutrons
.larger stable atoms have more neutrons than protons

Question 2

State 2 facts about unstable nuclei.

Answer 2

.an unstable nucleus may spontaneously change into a more stable nucleus
.a substance that contains atoms with unstable nuclei is radioactive

Question 3

How can an unstable nucleus change into a more stable nucleus?

Answer 3

by emmiting radiation in the form of a particle or a gamma photon - this is a random event that is not affected by a chemical reaction.

Question 4

What are alpha particles made of?

Answer 4

two protons and two neutrons.

Question 5

Describe alpha decay (7)

Answer 5

.a large nucleus is unstable if it has too many protons
.in the nucleus, the electrostatic force pushes protons apart
.if the force is big enough, an alpha particle is emitted from the nucleus
.an alpha particle is made of two protons and two neutrons
.it is emitted at a speed of about 15 000 000m/s
.the nucleus is pushed back the other way
.the atom is now a different atom

Question 6

When does beta-minus decay occur and what happens?

Answer 6

often occurs in nuclei with too many neutrons. A neutron in the nucleus changes into a proton and a high speed electron is emitted.

Question 7

When does beta-plus decay occur and what happens?

Answer 7

often occurs in nuclei with too many protons. A proton in the nucleus changes into a neutron and a high speed positron is emitted, which goes on to annihilate (destroy) with an electron.

Question 8

Describe beta decay (6)

Answer 8

.neutrons are unstable when they are not very close to protons
.they are more likely to be away from protons in a neutron rich nucleus
.an unstable neutron is likely to decay
.a beta particle is emitted, that pushes the nucleus backwards
.a beta particle is a high-speed electron created in the nucleus
.the atom is now a different element

Question 9

When does gamma decay occur and what happens?

Answer 9

often occurs after a nucleus has undergone another type of decay. The nucleus undergoes some nuclear rearrangement. Mass and atomic number remain the same because only energy has been released.

Question 10

What happens during neutron decay?

Answer 10

a neutron is emitted. The mass number decreases by one but the atomic number remains the same.