1.2 Flashcards
Atomic Number
a.no + proton number = number of electrons = bottom number
Mass number
m. no = number of protons + neutrons
Alpha
Helium nuclei
mass= 4
charge = 2+
Deflection = slight deflection towards the negative
Cannot penetrate skin
Beta
Fast moving electron
mass = 0
charge = -
large deflections towards the positive
Is stopped by metal sheets
Gamma
High frequency electromagnetic wave
mass= 0
charge=0
no charge=no deflection
Is stopped by lead
Beta equation when neutron changes into a proton
n0 >p+ + e- ^beta particle
(e- leaves nucleus)
Nuclear equation -
alpha emission
4/2 He
Mass no - down 4
atomic - down 2
Nuclear equation -
beta emission
0/-1 e
Mass - =
atomic- up 1
in the nucleus -
Neutron —-> Proton + e- ^ (ejected electron)
e- comes from the break up of a neutron
Nuclear equation -
Electron capture
P+ + e- —> N
Mass - =
Atomic - down 1
element + 0/-1 e —> new element
Nuclear equation -
Positron emission
0/+1 B+
Mass - =
atomic - down 1
Definition - Half life
This is the time taken for the radioactivity of an isotope to drop to half of its initial value
Rate of decay of radioisotope
Shorter the half life, faster the rate
Longer the half life, slower the rate
half life is inversely proportional to the rate
Effects of Alpha radiation
> tend not to be harmful unless it’s gas
radioactive gas can be breathed in , cause changes to cells = lung cancer
Effects of Beta radiation
> can penetrate skin anc travel several meters
more likely to harm body cells
Effects of Gamma radiation
> most harmful : high energy, greater penetrating power
can kill bacteria and micro-organisms (used to sterilise surgical instruments)
irradiate food, kill bacteria, increase shelf life
treat tumours
