Atomic structure Flashcards
what is in the nucleus of an atom
proton and neutron
where do electrons orbit
around the shells
what was JJ thompson a model of the atom
Plum pudding model
Ball of positive charge
with negative electrons embedded in it
What was rutherfords alpha scattering experiment
Fired positively charged alpha particles at a thin sheet of gold foil
Most went straight through however some deflected and some even came straight back off the foil
From these observations he concluded that Most of the atom was empty space ( due to going straight through)
The ones that deflected showed that the nucleus was positive as opposite charges repel
The ones that came straight back told him that the mass was concentrated in the nucleus
what does an alpha particle consist of
two protons and two neutrons
What happens to the alpha particle when it decays
4
He
2
e.g alpha decay in 16
K
8
= 12
K
6
loses 4 of the mass number
loses 2 from the atomic number
What is a beta particle
Fast moving electron
What’s a beta particles relative mass and mass number
0
what does a beta particle look like
0
e
-1
What does beta particles do to the atomic number( bottom number) in beta decay
Causes the bottom number to INCREASE BY 1
What are gamma rays
Waves
Does gamma rays cause any change to the number when in gamma decay
No
order the 3 from most ionizing to least
Alpha
Beta
Gamma (as it’s a wave)
Order it from most penetrating to least ( reverse )
Gamma
Beta
Alpha
what is alpha particles stopped by
thin sheet of paper
What is beta particles stopped by
Aliminium
What is gamma stopped by
Thick block of lead
as it’s the most penetrating
What is half life
time taken for radioactive nuclei in a sample to halve
what causes something to be radioactive
when it has unstable isotopes
What is Radioactive decay
When an unstable nucleus decays into another element and gives out radiation to become more stable
What is Activity
overall rate of decay of all isotopes
What is activity measured in
Bq Bequerels
Example question = the half life of a radioactive source is 40 hours. There are initially 3 million radioactive nuclei in a sample. How many nuclei will remain after 5 days
5 x 24h = 120h
120/ 40 = 3 half lifes
halve 3,000,000 3 times
What is nuclear fission
the splitting of large unstable nuclei into smaller nuclei
What happens in nuclear fission
An unstable fast moving neutron hits the unstable nuclei.
This causes the nuclei to become violently unstable and therefore split
These split into daughter nuclei
Two or three more neutrons explode out of the fission reaction and continues on
THIS IS KNOWN AS A CHAIN REACTION
what’s nuclear fusion
when two small light nuclei join together to make one heavy nucleus
Does fusion or fission Release more energy
FUSION
