Atomic Structure Flashcards
definition of relative atomic mass
average mass of its atoms compared to 1/12th the mass of carbon - 12
explain first step of mass spectrometry (electrospray)
ionisation: sample is disolved in solvent and pushed into machine via charged hypodermic needle. high voltage causes each particle to gain a H+
explain the second step of mass spectrometry
acceleration: all ions are accelerated at the same kinetic energy. lighter ions will experience greater acceleration
explain the third step of mass spectrometry
ion drift: ions move towards negative plate through the ion drift region
explain the fourth stage of mass spectrometry
detection: lighter ions hit the negative detector plate first, the ions gain an electron when they hit the detector. the movement of electrons induces a current. the current is proportional to the abundance of the atom
explain electron impact ionisation
sample is vaporised and bombarded with electrons. this knocks an electron off the molecule forming ions
what is the mass spectrum
a graph made by a computer with the data from the mass spectrometry
why are there lower peaks on the mass spectrum of electron impact data
as the atoms are bombarded by H+ ions it may cause the ion to produce fragments
how are electrons arranged
principle energy levels: 1,2,3,4. 1 being closest to the nucleus
each energy level is split into sub orbitals 1s, 2p,3d,4f
how are sub shells filled and emptied
the 4s sub orbital is filled before 3d as the 3d sub orbital is a high energy level than 4s
the 4s sub orbital loses electrons first
definition of ionisation energy
enthalpy change when one mole of gaseous atoms forms one mole of gaseous ion
equation for first ionisation energy
H(g) –> H+(g) + e-
three factors which affect ionisation energy
- nuclear charge: greater number of protons, greater attraction, greater the ionisation energy
2.atomic radius: greater distance, weaker attraction, lower the ionisation energy
3.shielding: greater number of shells, weaker attraction, lower the ionisation energy
why is the second ionisation energy greater than the first
during the first ionisation energy an ion is formed which increases attraction between remaining electrons and the nucleus
if there is a big jump in ionisation energy between ionisation 2 and 3 which group is the ion in
group 2, as the third electron removed is closer to the nucleus so has a stronger attraction explaining the large ionisation energy
