Atomic structure Flashcards
Relative atomic mass
the weighted mean of the mass of an elements atoms
to 1/12 the mass of carbon-12
Relative isotopic mass
the mass of an atom of an isotope
relative to 1/12 the mass of carbon-12
1st stage of mass spectrometry
ionisation
- particles are ionised via bombardment with high energy electrons
- generates positive ions
2nd stage of mass spectrometry
ions are accelerated by an electric field
3rd stage of mass spectrometry
deflection
- ions pass through strong magnetic fields
- lighter ions are deflected more
4th stage of mass spectrometry
detection
- ions are detected electronically as currents
- size of current indicates abundance
How is the mass of an isotope detected using time of flight
- all ions are accelerated so they have equal kinetic energy
KE = 1/2MV2 - ions with different velocities will have different masses
- velocity can be calculated using time and distance
What is the first ionisation energy definition
the energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions
Equation for 1st ionisation energy
X(g) -> X+(g) + e-
Factors that affect ionisation energies
- nuclear charge
- distance of outer electrons from nucleus
- shielding
What is the trend in ionisation energies across a period
increases
- greater nuclear charge so greater attraction between electrons and nucleus
What is the trend in ionisation energies down a group
decreases
- more shells so shielding and distance between nucleus and electrons increases
How many electrons does each quantum shell hold
1st - 2
2nd - 8
3rd - 18
What shape are s orbitals
spherical
What shape are p orbitals
dumbbell shaped
What is an orbital
an area in space that has a 95% chance of finding an electron
Explain why the 1st ionisation energy of group 2 is less than that of a group 3
the outermost electron from a group 2 is removed from an s subshell rather than a p subshell which is closer to the nucleus
Explain why the 1st ionisation energy decreases from phosphorus to sulfur
in sulfur the p electros are paired for the first time
- repulsions are set up between paired electrons
- this reduces energy needed to remove the electron
Which groups are in the s block
groups 1 + 2
Which groups are in the p block
groups 3 - 8
Which groups are in the d block
transition metals
How can you identify the group of an element from ionisation energies
big jumps in ionisation energies indicate that an electron is being removed from a subshell closer to the nucleus
group 1 - jump between IE 1 and IE 2
What is periodicity
chemical trends that repeat across periods
Which properties show periodicity
- melting and boiling points
- atomic radius