Topic P4 Atomic structure Flashcards
what did rutherford replace the plum pudding model with
the nuclear model
devloping model of atom
what are isotopes
different forms of the same element
what is alpha radiation
-when an alpha particles emitted from the nucleus
-2neutrons
-2protons
-do not penetrate far into materials and are stopped quickly
-only travel a few cm in air, and absorbed by a sheet of paper
-becuase of size are STRONGLY ionising
what is a beta particle
-fast moving electron released by the nucleus
-they have virtually no mass
-charge of -1
-moderately ionising, meaning they penetrate moderately far into materials
-absorbed by: aluminium
for every beta particle emitted a neutron in the nucleus is turned into a proton
what are gamma rays
waves of electromagnetic radiation, released by the nucleus
-penetrate far into materials
-travel a long distance through air
-weakly ionising as they pass through
-absorbed by thick sheets of lead
Nuclear equations
-show the radioactive decay by using element symbols
-written in the form
atom before decay—- atom after decay + radiation emitted
what does alpha decay do to the charge and masses of nucleus
decreases
as its made up of 2protons,2neutrons
protons positively charged whereas a neutrons neutral so charge decreases
what does beta decay do to charges
increases
-as the neutron in the nucleus turns into a proton and releases fast moving electrons
what do gamma rays do
-dont change the charge or mass of the nucleus
-as they only get rid of excess energy
how can radioactive substances be measured
with a Geiger-muller tube and counter
-which records the count-rate
what is half life
time taken for the number of radioactive nuclei in an isotope to halve
how to measure half life
by plotting a graph of activity against time
-found from the graph by finding the TIME INTERVAL on bottom axis corresponding to a HALVING of activity on the vertical axis
how can radiation bring risks
-as they enter living cells and ionise atoms within them
-damages cells, causing cancer or kill them
what is irridation
-exposure to radiation
