Radioactivity

Question 1

What is the SI unit for radioactivity?

Answer 1

Becquerel (Bq)

Question 2

Why is the mass found in the centre of the atom?

Answer 2

Because protons and neutrons are found inside the nucleus, the nucleus holds most of the atoms mass

Question 3

What is the use of symbols such as 12 C 6 to describe particular nuclei?

Answer 3

6 protons, +6 neutrons = atomic number
12 = total mass number

Question 4

Atomic (proton) number

Answer 4

is the number of protons in the nucleus of an atom

Question 5

Mass (nucleon) number

Answer 5

is the total number of protons and neutrons in the nucleus of an atom

Question 6

Isotopes

Answer 6

is an atom of the same element, i.e. it has the same number of protons/same atomic number, but has a different number of neutrons/different mass number.

Question 7

Alpha (α) particles

Answer 7

are high-energy particles made up of 2 protons and neutrons. And is usually emitted from nuclei that are too large. Their ionising power is very strong

Question 8

Beta (β−) particles

Answer 8

are high energy electrons emitted from the nucleus. And emitted by nuclei that have too many neutrons. Their ionising power is medium

Question 9

Gamma (γ) rays

Answer 9

are high energy electromagnetic waves
And are emitted by nuclei that need to lose some energy. Their ionising power is weak

Question 10

Investigation of penetrating powers

Answer 10

1. Connect the Geiger-Muller tube to the Geiger counter and measure the background radiation for over a minute
2. Repeat to get an average
3. Place the radioactive source 3cm away from the tube and take a reading over a minute
4. Take a set of absorbers: some paper, several different thicknesses of aluminium (increasing in 0.5mm intervals) and different thickness of lead
5. Place these absorbers between the source and the tube and take another reading over a one minute interval
6. Repeat with another radioactive source

Question 11

Alpha decay

Answer 11

· 2 protons and 2 neutrons are lost

· Mass number decreases by 4

· Atomic number decreases by 2

Question 12

Beta decay

Answer 12

· 1 neutron is converted to an electron (lost from the atom) and proton

· Mass number is unchanged

· Atomic number increases by 1

Question 13

Gamma decay

Answer 13

· Energy is lost from an atom in the form of an electromagnetic wave

· Mass number is unchanged

· Atomic number is unchanged

Question 14

How Geiger Müller detector detects radiation?

Answer 14

when connected to a counter, the detector will be able to measure radioactivity

Question 15

How a Photographic film detects radiation?

Answer 15

radiation will cause photographic film to darken

Question 16

Ionisation

Answer 16

is the process by which ions are formed by the gain or loss of electrons from an atom or molecule

Question 17

Background radiation on Earth

Answer 17

there are alot or rocks on Earth that contain radioactive substances, therefore we are constantly exposed to ionising particles

Question 18

Background radiation in Outer Space

Answer 18

we are exposed to cosmic rays which are isonising radiations in which our atmosphere protects us from. The two sources that make up the background radiation are: man made and natural

Question 19

Half-life

Answer 19

is the time taken for half the nuclei of that isotope in any sample of decay

Question 20

Radioactivity in Medicine

Answer 20

radioactive tracers help doctors to examine the insides of our bodies

Question 21

Radioactivty in Industry

Answer 21

radioactive tracers are used to detect leaks in underground pipes

Question 22

Contamination

Answer 22

the unwanted presence of materials containing radioactive atoms on other materials

Question 23

Irradiation

Answer 23

The process of exposing a material to alpha, beta or gamma radiation

Question 24

Dangers of Radiation

Answer 24

· Ionising radiation can damage human cells and tissues

· If the atoms that make up a DNA strand are ionised then the DNA strand can be damaged

· If the DNA is damaged then the cell may die, or the DNA may be mutated when it reforms

· If a mutated cell is able to replicate itself then a tumour may form

Question 25

How can uranium-235 atom be split?

Answer 25

during fission, U-235 atoms absorb loose neutrons. This causes U-235 to become unstable and split into two light atoms called fission products

Question 26

Nuclear fission as a source of energy

Answer 26

the process where heavy atoms are split into smaller, lighter atoms. This releases energy

Question 27

Radioactive decay as a source of energy

Answer 27

within the core of the Earth, radioactive isotopes of elements such as uranium, thorium and potassium provide a large proportion of the heat within the Earth through radioactive decay

Question 28

Isotopes

Answer 28

are atoms of the same element (or the same atomic number) and different mass numbers (different number of neutrons)