P4 ATOMIC STRUCTURE Flashcards
3 subatomic consistuents of an atom?
proton
neutron
electron
describe the arrangement of protons , neutrons and electrons in an atom
protons and neutrons = nucleus
electrons = energy levels around the nucleus
what type of charge does nucleus have?
positive because nucleus contains protons which have a positive charge and neutrons have no charge
2 ways that an atoms ‘s electron arrangement can be changed
absorbing electromagnetic radiation
emitting electromagnetic radiation
explain how an atoms’s electrons arrangement changes when its emits EM radiation?
The electron moves closer to the nucleus.
they move to a lower energy level
explain how an atoms electrons arrangement changes when its absorbs EM radiation?
electrons move further away from the nucleus
move to a higher energy level
what do all forms of the same element have in common?
same number of protons
how do atoms turn into positive ions?
lose one or more electrons on the outer shell
electrons are negatively charged so the resultant charge of the atom is positive
what may lead to a scientific model being changed or replaced?
discovery of new experimental evidence which doesn’t agree with the existing theory
prior to the discovery of the electron , what was believed about the atom?
atom was believed to be indivisible
which experiment led to to the plum pudding model being discarded?
rutherford’s alpha scattering experiment
what is the name given to the currently accepted model of the atoms?
bohr nucleus model
state the conclusions of the alpha scattering experiment?
most of the mass was in the nucleus
nucleus has a positive charge.
what reinforces a scientific theory?
when experimental results agree with the hypothesised theoretical calculations and theories
why do unstable nuclei give out radiation?
become more stable
as they release more radiation their stability increases
what is radioactive decay?
when an unstable nucleus gives out radiation as it changes to become more stable.
activity ?
the rate at which an unstable nucleus decays
unit for activity?
becquerel (bq)
count rate?
number of decays recorded each sec by a detector
an example of a detector that may be used to measure count rate?
geiger-muller tube
4 types of nuclear radiation?
alpha , beta , gamma and neutrons
structure of alpha particles?
2 neutrons
2 protons
same as helium nucleus.
structure of beta particles?
high speed electrons that are released from the nucleus
structure of gamma rays?
electromagnetic radiation that is released from the nucleus
put alpha beta and gamma radiation in order from most to least penetrating?
gamma , beta , alpha
put alpha , beta and gamma radiation in order from longest range in air to shortest range in air
gamma beta , alpha
put alpha , beta , gamma radiation from most to least ionising?
alpha , beta , gamma
state the materials that can stop alpha particles
skin , paper , a few centimetres of air
state the materials that can stop beta particles
aluminium foil
state the materials that can stop gamma rays
thick lead or concrete
give the symbol that represents alpha particles in nuclear decay equations
4
He
2
give the symbol that represents beta particles in nuclear decay equations
0
e
-1
what happens to the atomic number and mass number of nucleus when an alpha particle is released?
atomic number decreases by 2
the mass number decreases by 4
what happens to the charge of a nucleus when an alpha particle is released
charge decreases by 2
what happens to the atomic number and mass number of a nucleus when a beta particle is released
atomic number increases by 1
mass number stays the same
what happens in the nucleus when a beta particle is released?
a neutron turns into protons and releases beta particle
what happens to the charge of a nucleus when a beta particle is released?
increases by 1
what happens when the mass and charge of a nucleus when a gamma ray is emitted?
nothing it stays the same
state the word used to describe radioactive decay
random
define half life
the time taken for the number of nuclei , or count rate or activity of a sample to halve
describe 2 things we cannot know about radioactive decay?
do not know which nucleus will be next to decay.
do not know how long it will take for a specific nucleus to decay
radio contamination?
unwanted presence of materials containing radioactive atoms in other materials
irradation?
exposing an object to nuclear radiation. the object does not become radioactive
why is it important for the results of studies on the effects of radiation to be published and shared with other scientist.
to allow findings to be checked independently
this is known as peer review
state 5 precautions to take when using radioactive sources
keep sources in a lead lined box
wear face masks to prevent breathing in materials
wear gloves to prevent contamination of the skin
limit the time spent with radioactive sources
use tongs or robotic arms to handle sources to keep them far away from the body.
