Physical - Atomic Structure Flashcards
describe the plum pudding model
sphere of positive charge with small negative charges distributed within
which fundamental particles exist in the nucleus, giving it what charge?
protons and neutrons
positive
what is the relative mass of an electron?
1/1840
what must happen to each electron shell before the next one holds any electrons?
it must fill
state the formula for calculating the maximum number of orbiting electrons held by a shell
2(n²)
what is mass number? what letter represents it?
sum of protons and neutrons in an atom
A
what is atomic number? what letter represents it?
the number of protons in an atom
Z
what is the definition of relative atomic mass?
the mean mass of an atom of an element, divided by 1/12 of the mean mass of a atom of carbon-12
why is Mr the mean mass of an atom of an element, divided by 1/12 of the mean mass of a atom of carbon-12?
because it takes the relative abundances of the different isotopes of an element into account
what are isotopes?
atoms of the same element with the same atomic number (same protons and electrons) but with a different mass number (different neutrons)
what kind of isotopes react in the same way? why?
neutral isotopes
their atomic number and electron configuration is the same
what properties are different between isotopes? why?
physical properties
due to the different mass number
how are ions formed?
when an atom loses or gains an electron so it has an overall charge
what does time of flight (TOF) mass spectrometry assess?
the time it takes for ions of each isotope to reach a detector
what are the five main stages of TOF mass spectrometry?
ionisation
acceleration
ion drift
detection
analysis
what can mass spectrometry be used for?
To establish relative isotopic mass and relative abundance of isotopes
Identify elements
Determine relative molecular mass
In TOF mass spectrometry, describe the process of ionisation
sample of an element is vapourised and injected into the mass spectrometer where a high voltage is passed over the chamber, leaving +1 ions in the chamber
In TOF mass spectrometry, describe the process of acceleration
the positively charged ions are accelerated towards a negatively charged detection plate so they all have the same kinetic energy
In TOF mass spectrometry, describe the process of ion drift
Ions enter a region with no electric field so they drift through
Lighter ions drift faster than heavier ones
In TOF mass spectrometry, describe the process of detection
As lighter ions travel at higher speeds in the drift region, they reach the detector in less time than heavier ones
The detector detects charged particles and a mass spectrum is produced
In TOF mass spectrometry, describe the process of analysis
Mass spectrum is plotted
This plots mass/charge against abundance
what are orbitals?
clouds of negative charge that hold electrons
what are the first three orbitals?
s
p
d
what is the shape of the s-orbital?
spherical
what is the shape of the p-orbital?
dumbbell
how many electrons can an s-orbital hold before the next one is filled?
2
how many electrons can a p-orbital hold before the next one is filled?
6
how many electrons can a d-orbital hold before the next one is filled?
10
why are orbitals filled in the order s → p → d?
because the energy of the orbitals increases in this order
in terms of spin, how do electrons pair up?
electrons with opposite spin
which energy orbital is filled first?
the lowest energy one
what is the maximum number of electrons a single orbital can hold?
2
what is the definition of ionisation energy?
the minimum energy required to remove one mole of electrons from on mole of atoms in a gaseous state
why do successive ionisation energies typically require more energy than the first?
because as electrons are removed the electrostatic attraction between nucleus and outer electrons increases
what is the trend in first ionisation energies along a period?
increases due to decreasing atomic radius and so greater electrostatic forces of attraction
what is the trend in first ionisation energies down a group?
decreases due to increasing atomic radius and shielding which reduces the effect of electrostatic forces of attraction
when successive ionisation energies are plotted on a graph, what does a sudden large increase indicate?
a change in energy level
when successive ionisation energies are plotted on a graph, why is there a large sudden increase at a change in energy level?
because the electron is being removed from an orbital closer to the nucleus, which requires more energy, since the electrostatic force is stronger
what does the large increase in ionisation energy at a change of energy level provide evidence for?
atomic orbital theory
why is the first ionisation energy of aluminium lower than expected?
due to a single pair of electrons with opposite spin so there is natural repulsion, reducing the amount of energy needed to remove the outer electron
