p7 Flashcards
what are the three types of nuclear radiation
alpha
beta
gamma
what is radioactive decay like
random and is not affected by external conditions
what did scientists think the atom looked like at the start of the 20th century
sphere of positive charge with electrons buried inside
plum pudding
what did Rutherford, geiger and Marsden do
conducted an experiment where they fired alpha particles at very thin gold foil.
what happened when Rutherford, geiger and Marsden did the experiment
-most of the alpha particles passed straight through the foil. this means most of the atom is empty space
-some deflected through small angles which suggests the nucleus is charged
-a very small number deflected through large angles which suggests the nucleus has a large mass
what was created after the gold foil experiment
the nuclear model which says atoms have a positive nucleus and electrons orbit it
what is the atomic number
number of protons
what is the mass number
total number of protons and neutrons
what is an alpha particle
consist of two protons and two neutrons
charge of +2
what happens when an unstable element emits an alpha particle
atomic number goes down by 2 and mass number goes down by 4
what is a beta particle
high speed electron from the nucleus emitted when a neutrons changes to a proton and electron
what happens when an unstable element emits beta radiation
proton stays in the nucleus so atomic number goes up by 1
what happens when an unstable element emits gamma radiation
nothing it is an electromagnetic wave
what is ionisation
radiation from radioactive substances can knock electrons out of an atom and becomes positively charged
what does irradiated mean
if an object is exposed to ionising radiation but the object doesn’t become radioactive
