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LC Chemistry > Radioactivity > Flashcards

Radioactivity Flashcards

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1
Q

who discovered radioactivity

A

Henri Becquerel

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2
Q

how did henri becquerel discover radioactivity?

A

while studying uranium salts

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3
Q

what did the curies (mary + pierre) discover?

A

2 new radioactive elements: polonium and radium

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4
Q

what is alpha decay

A

helium nucleus

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5
Q

what is beta decay

A

fast moving electrons

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6
Q

how is beta decay formed

A

when a neutron is converted into a proton and an electron, and the electron is ejected from the nucleus

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7
Q

what is gamma decay

A

high energy electromagnetic radiation

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8
Q

what is alphas penetrating power

A

low- penetrates up to a sheet of paper/air

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9
Q

what is betas penetrating power

A

medium: penetrates up to 5mm of aluminium

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10
Q

what is gammas penetrating power

A

high-can penetrate up to a thick piece of lead

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11
Q

what is the mass of alpha

A

heavy

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12
Q

what is the size/mass of beta

A

light

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13
Q

what is the mass of gamma

A

not applicable as it is not a particle so it has no mass

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14
Q

what is the speed of alpha

A

slow (slowest of the 3)

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15
Q

what is the speed of beta

A

fast (faster than alpha

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16
Q

what is the speed of gamma

A

very fast: fastest of the 3

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17
Q

how does alpha deflect in a magnetic field

A

attracts to negative plate

18
Q

how does beta deflect in a magnetic field

A

attracts to positive plate

19
Q

how does gamma deflect in a magnetic field

A

no effect

20
Q

what are the uses of alpha

A

smoke detectors- americium 241

21
Q

what are the uses of beta

A

carbon-14 dating
iodine-131 measures iodine uptake by thyroid

22
Q

what are the uses of gamma

A

cobalt-60 used to sterilise medical equipment

23
Q

is alpha dangerous

A

only of inhaled or ingested will it cause cancer as it cannot penetrate skin

24
Q

is beta dangerous

A

yes. it can be absorbed by the skin and can cause sunburn but it is most dangerous when ingested or inhaled

25
Q

is gamma dangerous

A

yes. can penetrate skin easily and will cause cancer

26
Q

nuclear reaction

A

process that alters the composition, structure, or energy of an atomic nucleus

27
Q

give 3 differences between nuclear and chemical reactions

A

nuclear:
involves changes to the nucleus
a new element is formed
no chemical bonds are formed or broken

chemical:
involves electrons not the nucleus
no new elements are formed
chemical bonds are broken and formed

28
Q

radioisotopes

A

a radioactive isotope ie carbon-14

29
Q

radiocarbon dating

A

a technique used to determine the age of an object containing carbon. it is based on the ratio of carbon-14 to carbon-12 in the object

30
Q

explain how radiocarbon dating works

A

the ratio of carbon 12 to carbon 14 is constant in living organisms
when the organism dies no more carbon 14 is taken in and the carbon 14 already present in the organism decays. by measuring the ratio of carbon 12 to carbon 14 the age of the item can be calculated

31
Q

sources of background radiation

A

radon gas
nuclear weapons testing and accidents like Chernobyl

32
Q

what equipment is used when investigating radiation

A

geiger muller tube
rate meter
sheet of paper
5mm sheet of aluminium
alpha beta and gamma sources
blocks of lead

33
Q

what is a geiger counter?

A

a geiger muller tube and a rate meter joined

34
Q

what is a geiger muller tube

A

a sensing instrument used to detect radiation

35
Q

what does a rate meter do?

A

counts the number of radioactive particles that enter the GM tube per second

36
Q

what is the procedure when investigating radiation

A

measure background level of radiation
using a tongs and gloves hold alpha particle source close to the geiger muller tube
note increase in radiation detected
hold sheet of paper between alpha and GM tube
number of radiation detected should drop
repeat for beta (replacing sheet of paper with aluminium) and gamma (replacing sheet of paper for a block of lead)

37
Q

explain why it is impossible to change Pb into Au by a chemical reaction

A

chemical reactions involve electrons only and do not involve changes to the nucleus
changing Pb into Au requires a nuclear reaction to alter the number of protons in the nucleus

38
Q

write the general formula for an alpha decay reaction

A

a 4 (a - 4)
X——> He + (X-2)
z 2 (z - 2)

39
Q

write the general formula for a beta decay reaction

A

a 0 (a )
X——> e- + (X+1)
z -1 (z + 1)

40
Q

half life

A

time taken for half of the nuclei in a given radioactive sample to decay

41
Q

how do you calculate half life

A

1.divide how many years its asking for divided by the half life
2. divide the amount in the sample by 2 to the power of your answer in 1.

LC Chemistry (22 decks)

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