Unit 1.2 Flashcards
Radioactivity
Alpha?
4 He
2
2 protons + 2 neutrons
charge of 2+
most harmful in the body - can’t get through the skin
least penetrating
most ionising
stops with either a sheet of thin paper or a few cm of air
ionising def?
collides with other molecules, knocking off eelectrons
deflected towards a negative plate in a magnetic field
deflected by a magnetic field according to Flemmings left hand rule
Example of Alpha?
234 U —- 234 + 4 He
90 90 2
Beta?
stream of high energy electrons which = negatively charged
moderately penetrating
moderately ionising
in a magnetic field, its directly opposite deflected than alpha
in an electric field, its deflected towards a positive plate
1 mm of air
5 mm of Al
Equation for beta?
14 C —- 14 N+ 0 B
6 7 -1
Gamma?
electromagnetic wave of high energy
high energy electromagnetic radiation with no charge
not deflected with an electric or magnetic field
weakly ionising but strongly penetrating
can pass through several cm of lead
Inverse Beta decay?
electron capture
an orbital electron is captured by a proton in the nucleus and forms a neutron which releases an electron neutrino
Equation for this>
40 K + 0 e ——– 40 Ar
19 -1 18
one place to the left
Inverse beta decay?
B-
Beta positive decay?
proton emission
Proton = converted to a neutron, releasing a positive positron
( positive electron)
Example?
23 Mg —- 23 Na + 0 B+
12 11 -1
what is half life?
the time taken for half of the atoms in a radioisotope to decay or to fall to half of their intial value
there are 2 types of half equations
the time taken to fall to a fraction of its intial value
finding the mass after a given time
Example?
28 Mg ‘s Half life = 21 hours
how long until it falls to an 1/8th of its value?
1— 1/2 —- 1/ 4—– 1/8
takes 63 hours
example 2
if you start with 2g of Mg, how much remains after 84 hours?
84/21 = 4 hours
2 — 1/2 — 1/4 —– 1/8
1/8 of a gram = 0.125 g
