P4 - Atomic Structure Flashcards
What did John Dalton do
Said matter was made up of tiny spheres. Each element was a different atom
What did JJ Thomson do
Discovered electrons that could be removed from atoms. > spheres of positive charge with electrons in them ‘plum pudding model’
What did Rutherford do
Beam of alpha particles at thin gold foil. Some deflected but most went straight through. Some deflected as they hit the tiny nucleus - mainly empty space in atom
What did niels Bohr do
Electrons orbit at certain distances ‘energy levels’
What did James Chadwick do
Proved neutron existence > imbalance between mass and atomic number
Key information on atoms
Nucleus makes up most of mass - protons and neutrons
No overall charge as protons = electrons and cancel the charge out
Electrons can move or leave energy levels. Gain energy from EM radiation - higher level = further from nucleus
What are isotopes
Different forms of the same element
Isotopes of an element are atoms with the same number of protons but different number of neutrons
What do unstable isotopes try to do
They tend to decay into other elements. They give out radiation to become stabler (balance protons and neutrons or get rid of excess energy) ‘radioactive decay’
What do radioactive substances spit out
Spit out types of ionising radiation from nucleus - alpha beta or gamma
What is ionising radiation
Radiation that knocks electrons off, creating positive ions
Key information of alpha particles
They are helium nuclei (they’re the weird fish symbol or proportional to)
Alpha radiation is when an alpha particle is emitted from the nucleus. It is 2 neutrons and 2 electrons.
Don’t penetrate far into materials - stopped quickly
Only travel a few cm in air (absorbed by paper)
Size = strongly ionising
Beta particle key information
They are high speed electrons released from nucleus (they’re the German B for ‘ss’)
Have no mass and a charge of -1
Moderately ionising - penetrate moderately far and have a few metres in air (absorbed by aluminium sheet)
For every beta particle emitted, a neutron turns to a proton
Key information for gamma rags
They’re EM waves with a short wave length
Weird Y symbol
EM radiation released from nucleus
Penetrate far and travel long distance in air.
Weakly ionising as they pass through rather than colliding (absorbed by thick lead sheets)
What are nuclear equations
A way of showing radioactive decay
It’s written as
Atom before decay - > atom after decay + radiation emitted
What do alpha particles do if emitted
If an atom emits alpha particles, atomic number reduces by 2 mass reduces by 4 as it’s 4 He
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