Topic 4 – Atomic Structure Fundamentals Flashcards
whats the radius of an atom
1 x 10^-10 m
the radius of the nucleus is __________ the radius of the atom
less than 1/10000
where do we find electrons
energy levels
energy levels which are further from the nucleus are at a ____________ than those close to the nucleus
higher energy level
how can an electron change energy levels to move to a higher energy level
if the atom absorbs electromagnetic radiation
how can an electron change to a lower energy level?
if the atom emits electromagnetic radiation it can return to a lower energy level
What is the mass number
the larger number, protons + neutrons
why do atoms have no overall charge?
number of electrons is equal to number of protons
so negative charges in electrons cancels out positive charge in protons
whats the atomic number
number of protons/electrons
how to calculate neutrons?
subtract atomic number from mass number
whats an isotope
when atoms of the same element have diff nos of neutrons
what did the ancient greeks believe about atoms?
everything was made of atoms. atoms were tiny spheres which couldn’t be divided
why was the discovery of electrons important
it showed atoms are NOT spheres that can’t be divided. they have an internal structure.
what was the plum pudding model
ball of positive charge w/ negative electrons embedded in it
describe the finding of the alpha particle scattering experiment
most particles went straight through the gold meaning atoms are mostly empty space (pp models wrong)
some atoms were deflected meaning centre of the atom must have a positive charge that repelled the alpha particles
some particles bounced straight back so the mass of the atom must be concentrated in the centre.
what did scientists replace the plum pudding model with?
The nuclear model
what did niels bohr sugges t
electrons orbit the nucleus at specific distances (now called energy levels)
why was niels bohrs theory accepted?
Bohrs work agreed with the results of experiments by other scientists
what was the order of discovery?
electrons, protons, neutrons
what is radioactive decay
when isotopes have an unstable nucleus so the nucleus gives out radiation to become stable.
radioactive decay is a _____ process
random
what is activity and what unit is it measured in?
the rate at which a source of unstable nuclei decay
measured in becquerels (Bq)
1Bq = 1 decay per second
what is the countrate
the number of decays recorded each second by a detector .
whys the countrate different to activity?
Background radiation
