P5 complete Flashcards
Who was John Dalton?
He proposed that matter was made up of atoms which couldn’t be broken up.
Who was J.J. Thompson?
Discovered particles called electrons that could be removed from atoms, so proved Dalton wasn’t quite right.
What did Rutherford discover via his experiment?
He fired a beam of alpha particles at thin gold foil.
- as some particles deflected back (which wasn’t expected) it suggested there was something in the centre of the atom, which went against the original model.
- this led to the theory of the positively charged atom.
Name some features of the modern model of the atom.
- Tiny nucleus at the centre, contains protons and neutrons giving an overall positive charge.
- Rest of atom mostly empty space.
- Negative electrons move around the outside of the nucleus.
What are isotopes?
Different forms of the same element.
-all isotopes have the same number of protons
What determines the identity of an element? Where is this located on an element.
Number of protons in atom. Number of protons = atomic number (Smaller number)
How do you work out the mass number? bigger number
Number of protons + number of neutrons.
What do isotopes have?
Same number of protons but a different number of neutrons giving the same element a different mass number.
What does ionising radiation do to the atom?
knocks off electrons creating positive ions.
What is alpha radiation?
Highly ionisation
Lowly penetrating
2 neutrons and 2 protons.
Big, heavy and slow
What is beta radiation?
Medium penetration and ionisation
1 electron
Fast and small.
What is gamma radiation?
Lowly ionising, highly penetrating.
-no mass or charge, transfer energy.
What stops alpha particles?
“ beta
“ gamma
Paper
Thick aluminium
Thick lead
What happens when you emit alpha particles?
Mass decreases by 4 (2neutrons+2protons)
Atomic number decreases by 2protons.
What happens when you emit beta particles?
Mass doesn’t change
Atomic number increases by 1
