Atomic Structure Flashcards
What was the first atoms
Solid spheresJohn dalton
1803
describe plum pudding model
Ball of positive charge with electrons scattered within it
Jj Thompson
1897
Describe nuclear model
Mass is concentrated at centre and nucleus is charged
Most atoms are empty space
1909
Ernest Rutherford
What did Neil’s Bohr discover
Theorised electrons were in shells orbiting nucleus at certain energy levels
1911
Describe the atomic structure we have today
James Chadwick
1932
Discovered neutrons in nucleus
What is an isotope
An element with same number of protons but different number of neutrons
What do isotopes do if they’re unstable
Decay and give out radiation
Ionising radiation can knock electrons off atoms
What happens to unstable isotopes
Decay into other elements and give our radiation as they try to stabilise
Spit out a or more ionising radiation from nucleus
Explain alpha radiation
Made of two protons and two neutrons (helium nucleus )
Range is 10 cm
Stopped by paper or skin
Strongly ionising
Describe beta radiation
Made of high speed electrons from nucleus
Range 1 metre
Stopped by thin aluminium
Moderately ionising
Describe gamma radiation
Electro magnetic radiation from nucleus
Range 1 km
Stopped by tick lead
Very weakly ionising
What are the dangers of using ionising radiation
Can enter living cells and ionise atoms within
Can damage and cause cancer or kill of completely
What is half life
Time taken for number of radioactive nuclei in isotope to half
What is irradiation
Occurs when materials are near radioactive source
How to answer alpha decay questions
Made of 2 protons and 2 neutrons
Atomic number goes down by 2 and mass number by 4
