P4 ATOMIC STRUCTURE
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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