Atomic structure Flashcards
Model of the atom?
1804 - Dalton - Solid Sphere Model
1900 - Thomson - Plum Pudding Model
1909 - Rutherford - Nuclear Model
1913 - Bohr - Planetary Model
1926 - Schrodinger - Quantum Model
Describe the current model of the atom:
the nucleus is tiny but makes up most of the mass of the atom
It contains protons and neutrons, with electrons on the outer shells
the number of protons = the number of electrons
As the protons and electrons have equal but opposite charges, atoms have no overall charge
What is an isotope?
Isotopes are different forms of the same element. They have the same number of protons but a different number of electrons to the original element.
How is mass number linked to protons and neutrons?
mass number of atom = number of protons + number of neutrons
Describe Alpha particles:
they do not penetrate very far in materials
they can only travel a few cm in air and can be absorbed by paper
they are strongly ionizing due to their size
describe beta particles:
it is a fast moving electron released by the nucleus
they are moderately ionizing
they penetrate moderately far into materials before colliding
they can travel a few m in the air and can be absorbed by aluminum
describe gamma rays:
they can penetrate far into materials without being stopped
They can travel a long distance through the air
they are weakly ionizing because they tend to pass through rather than collide atoms
They can be absorbed by thick sheets of lead or m of concrete
What is a nuclear equation?
Nuclear equations are a way of showing decay, for example:
atom before decay -> atom after decay + radiation emitted
Alpha decay
Alpha particles are made up of two protons & two neutrons
when an atom emits an alpha particle its atomic number reduces by 2 and its mass reduces by 4
a proton is positive and a neutron is neutral, so the charge decreases
in nuclear equations, an alpha particle can be written as helium nucleus
Beta decay:
beta decay increases the charge of the nucleus
a neutron in the nucleus turns into a proton, releasing a beta particle
the number of protons increases by 1, increasing the atomic number
because the nucleus has lost a neutron and gained a proton, the mass does not change.
a beta particle is written as (0) / (-1)e
Gamma rays:
gamma rays are a way of getting rid of excess energy from the nucleus
This means there is no change to the atomic mass or atomic number
What is half life?
Half - life can be used to find the rate at which a source decays - its ACTIVITY. Activity is measured in becquerels, Bq (where 1 Bq is 1 decay per second)
What is background radiation?
background radiation is low level radiation around us. You should calculate this and subtract from results to avoid errors. it is made up of 3 main things:
radioactivity from naturally occurring unstable isotopes
radiation from space - cosmic rays
radiation due to human activity
what is exposure to radiation called?
Irradiation - irradiating something doesn’t mean it is radioactive
What is contamination?
It is radioactive particles getting onto objects, these objects can then release radiation which may cause harm to you.
