Atomic Structure Flashcards
What are isotopes?
Atoms with the same number of protons but different number of neutrons
Name 2 ways a sample can be ionised
1) Electron impact
2) Electrospray ionisation
Describe the process of electron impact
1) Vaporised sample injected at low pressure
2) Electron gun fires high energy electrons at sample
3) Knocking out an outer electron
4) Forming positive ions with different charges
Describe the process of electro spray ionisation
1) Sample dissolved in highly volatile solvent
2) Injected through fine needle with high voltage at the end
3) Sample gains a proton, increasing mass
4) Sample moves towards negative plate
Give the equation for electro spray ionisation
M(g) + H+ –> MH+(g)
How are positive ions accelerated?
By an electric field to a constant KE
What happens in the flight tube?
1) Positive ions with smaller m/z value have same KE and those with larger m/z value, so move faster
2) Heavier particles take longer to move through drift area
3) Ions are distinguished through different flight times
How are ions detected?
1) Ions reach detector and generate small current (produced by electrons transferring from detector to positive ions)
2) Computer analyses current
3) Size of current is proportional to abundance of species
What is m/z?
Mass/charge ratio
What order off sub shells do atoms fill up?
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p
What is the rule for d-block elements forming ions when writing the electronic configuration?
Lose electrons from 4s before 3d
Write the electronic configuration for a Zn2+ ion (28 electrons)
1s2 2s2 2p6 3s2 3p6 4s0 3d10
Define first ionisation energy
Enthalpy change when one mole of gaseous atoms is formed from one mole of gaseous ions with a + charge
Write the equation for first ionisation energy
H(g) –> H+(g) + e-
Define second ionisation energy
Enthalpy change when one mole of gaseous ion with 1+ charge forms one mole of gaseous ion with 2+ charge
Write the equation to show second ionisation energy
Ti+(g) –> Ti2+(g) + e-
Describe 3 factors affecting ionisation energy
1) Attraction of nucleus
- More protons in nucleus –> greater attraction)
2) Distance of e- from nucleus
- Bigger atom –> outer e- further from nucleus –> weaker attraction to nucleus
3) Shielding of attraction of nucleus
- e- in outer shell is repelled by e- in complete inner shells –> weakens attraction of nucleus
Why is the second ionisation energy always bigger than the first?
1) When first e- is removed, a positive ion is formed
2) Ion increases attraction on remaining e-, so energy required to remove next e- is higher
Why do first ionisation energies decrease down a group?
Outer e- are found in shells further from nucleus, so are more shielded and attraction of nucleus is smaller
How do you calculate the mass of an ion (kg)
(Atomic number of ion x 10^-3) / (6.022 x 10^23)
