Revision topic 17

Question 1

explain the “key” discovery that Henri Becquerel

Answer 1

Henry discovered an image of a key on a film he developed, he realized that uranium salt was on top of that key, so he concluded that the uranium salt had produced some form of radioactivity that went through the paper but not the key leaving an image of the key then he had Marie Curie research more about it

Question 2

what are the two types of radiation that Ernest Rutherford discovered

Answer 2

1. alpha radiation

2. beta radiation

Question 3

why are some substances radioactive

Answer 3

because they would have an unstable nucleus that would decay and emit radiation, the action of one nucleus to become unstable is completely random

Question 4

what is background radiation?

Answer 4

it is ionizing radiation from radioactive substances in the environment, in space, and man-made sources

Question 5

what did Ernest Rutherford deduce from his experiments?

Answer 5

he deduced that there is a nucleus:
at the center of every atom that is much smaller than the atom because alpha particles passed by

where most of the mass of an atom is located

Question 6

why was rutherford’s nuclear model quickly expected?

Answer 6

because it agreed with the calculations that Marsden and Geiger did, and it explained radioactivity in terms of changes that happen to an unstable nucleus once it emits radiation, and it predicted the existence of a neutron

Question 7

an unstable nucleus becomes more stable by?

Answer 7

being emitting alpha, beta, or gamma particles

Question 8

what does an alpha particle consist of?

Answer 8

2 positive protons and 2 nuetrons

Question 9

what are beta particles?

Answer 9

it is an electron created and emitted by a nucleus that has many neutrons compared to protons

Question 10

what are the relative mass and relative charge of a beta?

Answer 10

beta particles have a relative mass of 0 but a relative charge of -1

Question 11

what is alpha radiation stopped by?

Answer 11

a thin sheet of paper

Question 12

what is beta radiation stopped by?

Answer 12

aluminum sheet

Question 13

what is gamma radiation stopped by?

Answer 13

thick lead sheet or concrete

Question 14

what is ionization

Answer 14

is the process of radioactive substances knocking electrons down out of an atom and the atom becomes charged

Question 15

what is an irradiated substance

Answer 15

a material thats have been exposed to ionizing radiation

Question 16

the activity of a radioactive isotope is?

Answer 16

the number of atoms that decay per second

Question 17

what is a count rate of a sample

Answer 17

the number of counts per second

Question 18

what is the half-life of a radioactive isotope?

Answer 18

it is the average time it takes for the number of nuclei of an isotope in a sample to halve

Question 19

explain how carbon dating is used to determine the age of an ancient wood

Answer 19

living wood contains a tiny portion of radioactive carbon, when the trees die the number of radioactive carbon decreases, so to find the age of the tree we compare the count rate of the sample with a living wood about the same mass

Question 20

explain how uranium dating is used to determine the age of igneous rock

Answer 20

the rock contains radioactive uranium that decays into the lead so the scientist would measure the number of lead atoms and uranium atoms

Question 21

what is nucluer fission

Answer 21

it is the splitting of the atomic nucleus into two smaller nuclei releasing 2 or 3 neutrons and energy

Question 22

how does nuclear fission occur

Answer 22

it occurs when uranium-235 or plutomium-239 absorbs a neutron and the nucleus splits

Question 23

whats a chain reaction

Answer 23

it’s an event that occurs in a nuclear reactor and happens when each fission event causes further fission events

Question 24

whats does the reactor core contain

Answer 24

fuel rods, control roads, and water and high pressure

Question 25

what is the job of the water in a nuclear reactor

Answer 25

it acts as a moderator that slows down the fission neutrons, it also acts as a coolant to transfer the kinetic energy generated to the heat

Question 26

what is the job of the control rod in a nuclear reactor

Answer 26

they absorb the neutrons to control the chain reactions

Question 27

what is nuclear fusion

Answer 27

when two small nuclei release energy when they fuse together to form larger nuclei,

Question 28

how does fusion happen in the sun

Answer 28

two protons fuse forming heavy hydrogen, then another two protons would do the same thing, after that the two heavy hydrogens would fuse forming helium nuclei and with each fusion energy is realized

Question 29

whats is the most ionizing radiation

Answer 29

alpha followed by beta then gamma