Ch8 Radioactivity

Question 1

Who discovered radioactivity

Answer 1

Henri becquerel

Question 2

What did becquerel find

Answer 2

Radiation was emitted continuously and didn’t require that the uranium be treated with light or heat - ie it was spontaneous

Question 3

What did henri becquerel observe

Answer 3

That some sort of radiation emitted by uranium was able to penetrate paper and affect a photographic plate

Question 4

What did henri becquerel do

Answer 4

Left some uranium salts resting on a photographic plate that was wrapped in black paper.
Photographic plate became fogged or darkened in the area near uranium salt

Question 5

Ore becquerel used

Answer 5

Pitchblende

Question 6

Two scientists and the elements they discovered

Answer 6

Marie and Pierre curie
Radium polonium

Question 7

Radioactivity

Answer 7

The spontaneous breaking up of unstable nucleus with the emission of one or more types of radiation.

Question 8

3 types of radiation

Answer 8

Alpha particles
Beta particles
Gamma radiation

Question 9

Alpha particles

Answer 9

• groups of 2 protons and 2 neutrons emitted from unstable nucleus
  I.e. the same as the nucleus of a helium atom 4 2 He

Question 10

Alpha particles characteristics

Answer 10

-charge positive 2
-attracted to negative electrode
-have a relatively large mass, travel relatively slow
-low penetrating power, stopped by sheet of paper or few cm of air

Question 11

Alpha emitter

Answer 11

Americium-241
Polonium-210

Question 12

Americium-241

Answer 12

Used in smoke detectors
As alpha particles have low penetrating power, smoke alarms do not pose health risks

Question 13

Polonium-210 poisoning

Answer 13

Alexander Litvinenko
If radioisotopes that emit alpha particles are inhaled or ingested -> harmful

Question 14

Beta particles

Answer 14

• Beta radiation resulst when within a nucleus a neutron splits into a prótón and an electron
• prótón States in nucleus; electron is ejected from the nucleus
  High speed, high energy electron

Question 15

Beta particles characteristics

Answer 15

-Negative, attracted to positive electrode
-Lighter than alpha particles and are more penetrating therefore
-can penetrate up to 5mm of aluminium

Question 16

Beta particles emitter

Answer 16

Carbon-14

Question 17

Carbon-14

Answer 17

Used to find the age of objects -> carbon dating

Question 18

What did radioactivity dismiss

Answer 18

Daltons theory that atom was a solid sphere

Question 19

How did the discovery of radioactivity show that the atom is not a solid sphere, but consists of smaller particles?

Answer 19

The only place alpha and beta particles could be coming from is from within the atoms of the radioactive material.

Question 20

Gamma radiation

Answer 20

• High energy electromagnetic radiation… sim to X-rays

Question 21

Gamma radiation characteristics

Answer 21

• does not consist of particles (does not have mass)
• does not consist of charged particles - not deflected by electric or magnetic fields
  -unstable nucleus emits gamma radiation in order to lose surplus energy

Question 22

Gamma radiation characteristics

Answer 22

• High penetrating ability - only stopped by thick slab of lead
  -most dangerous type of radiation

Question 23

What can gamma radiation be used for

Answer 23

-can change the structure of the chemicals in our bodies and cause cancer.
-can be used to kill cancer cells by focusing the radiation on the cancerous tissues.

Question 24

Gamma radiation emitter

Answer 24

Cobalt - 60
Used in hospitals -> gives off gamma rays

Question 25

Used to detect radioactive radiation

Answer 25

Geiger - Müller tube -connected to ratemeter -detects a,b,y radiation

Question 26

Nuclear reactions

Answer 26

Process that alters the composition, structure or energy of an atomic nucleus. -radioactive radiation is emitted from the nuclei of unstable atoms… nuclear reaction!

Question 27

Chemical reactions vs nuclear reactions

Answer 27

Chemical - involves electrons rather than nucleus Nuclear - changes take place in nucleus and electrons not involved Chemical - no new element formed/ nuclei of atoms stay same Nuclear - new element formed from change in nucleus of an element - transmutation Chemical - no release of nuclear energy Nuclear - nuclear energy released Chemical - chemical bonds broken and formed Nuclear - no chemical bond breaking or bond formation involved

Question 28

Alpha decay

Answer 28

Atom loses 2 protons and 2 neutrons from its nucleus -atomic no. Decrease by 2 -atomic mass decrease by 4

Question 29

Beta decay

Answer 29

When an atom loses a beta particle, the b particle is ejected from the nucleus -neutron is changed into a proton and an electron -atomic no increase by 1 -mass number no change

Question 30

Emission of gamma radiation

Answer 30

Loss of gamma radiation does not give rise to any new atoms -energy simply lost from the nucleus

Question 31

Half- Life

Answer 31

Of an element is the time taken for half of the nuclei in any given sample to decay -emission of radiation is random -each radioisotope decays at its own rate QUITE VARIED

Question 32

What is used to find half lives

Answer 32

Geiger- Müller tube and ratemeter

Question 33

Where can radioactive elements be found

Answer 33

In the lanthanides and actinides series

Question 34

Radiocarbon dating

Answer 34

Carbon dating A technique used to determine the age of an object containing carbon -based on the ratio of carbon -14 to carbon-12 in the object

Question 35

Background radiation

Answer 35

Naturally occurring radiation in our environment (Radon gas produced by decay of uranium and thorium in rocks)

Question 36

Uses of radioisotopes

Answer 36

-medical uses - radiotherapy, sterilise medical equipment, (gamma radiation) -archaeology - carbon 14 dating -agricultural research - eg study uptake of fertilisers by plants -food irradiation - kills germs -industry

Question 37

Radioisotope

Answer 37

Radioactive isotope