P4-Atomic structure Flashcards
What was the Necleur model and to discover it
Scientist in Rutherford Lab tried firing a beam of alpha particles at a thin gold foil And expected for particles to pass straight through – however most particles would affect more than expected and if you were deflected back the way They had come
-This meant that most of the mass had to be concentrated at the centre of the atom in a tiny nucleus – this also have to be positive as it repelled the positive alpha particles
– it also meant that nearly all the Atom is empty space
What was the plum pudding model and who discovered it
JJ Thompson
– he discovered particles called electrons that be removed from atoms – he suggested that atoms was spheres of positive charge with tiny electrons stuck in them like fruit in a plum pudding
To develop the current model of the atom and what did they find
Current model – Neils Bohr suggested that electrons orbit the nucleus at certain distances
– he also found protons which had the same positive charge That added up to the overall charge of the nucleus
20 years later James Chadwick prove this distance of the neutron which explain the imbalance between atomic and the mass numbers
What is the current model of the atom
-the nucleus is tiny but makes up with most the mass of the atom
-It contains protons which are positively charged and neutrons which have a charge of zero, which gives an overall positive charge
– the rest of the atom is empty space
– negative electrons orbit around the outside of the nucleus really fast
In the atom what is equal to what
Protons equals electrons
What are alpha particles And what traits do they have
They are helium nuclei (two neutrons and two protons)
– It has a high ionising power – as a low penetration power – It has a mass of four atomic units – has a charge of +2 -It can be stopped by paper -They can only travel a few centimetres in air
What are beta particles and what traits they have
They are the same as an electron – it has a mass of 1/2000 of a proton – has medium penetration power – it has medium ionising power – It can’t be stopped by aluminium -They have a range of a few metres in air
What are gamma rays and what rate they have
They are a wave – has no charge – has the least ionising power – has the highest penetration power – has no mass – it’s stopped by lead -They travel a long distance in air
What is a half life
The time taken for the number of radioactive nuclei in an isotope to half
What is radioactive decay
And unstable nucleus becomes more stable by emiting alpha, beta or gamma
What is activity
The number of unstable atoms that Decay per second
What is counter rate
The number of counts per second detected by a Geiger counter
What is dangerous about ionising radiation
Can enter living cells and ionise atoms within them. This can damage the cells which can cause cancer or kill them off completely
How do smoke alarms Use radiation to work
Smoke alarms contain a radioactive isotope that sends out alpha particles into a gap in to a circuit an alarm . The particles ionised in the air in the gap so there is the current across the gap, any fire the smoke absorbs the ions in the current across the gap and the alarm sounds
What is irradiation
This means that they’re exposed to the radioactivity
