Radioactivity + Atomic Structure

Question 1

Define activity

Answer 1

The activity of a radioactive sample is the rate of which nuclei will decay or disintegrate

Question 2

Write an equation for B- decay

Answer 2

_

d —-> u + e-1 + V

Question 3

Write an equation for B+ decay

Answer 3

u —–> d + e+1 +V

Question 4

Define the decay constant

Answer 4

The decay constant is the probability that an individual nucleus will decay per unit of time

Question 5

Define half-life

Answer 5

The half life of a radioisotope is the mean time taken for half of the active nucleus to decay

Question 6

Define an isotope

Answer 6

An isotope is nuclei of the same element with different number of neutrons but the same number of protons.

Question 7

State 3 types of ionizing radiation produced from a radio active sample and which is most ionizing

Answer 7

The 3 types are alpha particles, beta particles and gamma rays. The most ionizing and least penetrating is alpha particles, therefore the least ionizing is gamma rays and they are the most penetrating

Question 8

How are alpha, beta and gamma emissions affected by electric fields and magnetic fields

Answer 8

Since gamma rays have no charge they pass through deflected, both alpha and beta particles have a minus charge however as beta particles have a lower mass than alpha they are deflected more by both fields

Question 9

Why is decay considered random

Answer 9

1) The decay of a nucleus is not affected by the presence of another nuclei
2) The decay is not affected by external factors eg, temp

Question 10

Why is decay considered spontaneous

Answer 10

1) It is impossible to predict when a nucleus will decay

2) All nuclei in a sample have the same chance of decaying per unit time

Question 11

Write the mathematical decay equation

Answer 11

-lamba x t
N=N e
0

Question 12

State a couple of limitations of carbon-dating

Answer 12

1) The technique can only be used on material that is over a century old
2) Modern living tissue has less C 14 present
3) There is a small uncertainty with the half life of C 14

Question 13

State the relationship between decay constant and half-life

Answer 13

lambda x t = 0.693

0.5

Question 14

State the charge on an up and down Quark

Answer 14

Up quark = +2/3 e

down quark = -1/3e

Question 15

What are hadrons

Answer 15

Hadrons are a family of subatomic particles affected by strong nuclear force, such as protons and neutrons

Question 16

What are leptons

Answer 16

Leptons are a family of subatomic particles, that are unaffected by the strong nuclear force

Question 17

Describe how the alpha scattering experiments provide evidence for the existence, charge and size of the nucleus

Answer 17

Alpha particles were fired in a beam towards a thin gold foil, the alpha particles either passed straight through unaffected to detector showing that the nucleus consisted of empty space, there were also deflected , suggesting there was a bigger mass inside the atom or they were reflected, this showed the nucleus had a positive mass , and was tiny in comparison to the diameter of the atom, and the nucleus was located in the center of the atom

Question 18

Describe the nature and range of the forces acting on the protons and neutrons in the nucleus

Answer 18

The first force acting on the protons and neutrons is the strong nuclear force, this force has an attractive nature to attract protons and neutrons together, and occurs over a short range. A second force is the electrostatic force this force can be either attractive or repulsive but is usually attractive at a long distance and repulsive at short distances. The final force is gravitational force, this force is attractive and occurs over a long distance.