1.1 Atomic structure Flashcards
(16 cards)
What are the 4 stages of mass spectrometry?
- ionisation, acceleration, separation of ions, detection
Define relative atomic mass:
- the weighted average mass of all the isotopes, relative to 1/12th of the mass of 1 atom of C-12
How are ions accelerated in a mass spectrometer?
- using an electric field
- they are all accelerated with the same KE
How are ions detected and abundance measured in a mass spectrometer?
- ions gain an electron at the detector which generates a current
- the size of the current is proportional to the abundance of the ion
Describe the process of electron impact ionisation:
- the sample is injected into the spectrometer and vapourised
- an electron gun fires high-energy electrons at the sample
- the high-energy electrons knock an electron off the particles in the sample to form + ions
Describe the process of electrospray ionisation:
- the sample is dissolved in polar volatile solvent
- injected through a fine hypodermic needle to produce a fine mist
- needle tip is attached to the positive terminal of a high voltage power supply
- particles gain a proton (H+ ion) from the solvent to form positive ions
Why do successive ionisation energies increase?
- number of protons stays the same but is attracting fewer and fewer electrons
- shielding decreases
- nuclear attraction on the outer electron increases
Give the net equation for the 4th ionisation energy of Mg:
- Mg (g)»_space;> Mg4+ (g) + 4e-
Give the electronic figuration of chromium (Cr):
*1s2, 2s2, 2p6, 3s2, 3p6, 3d5, 4s1
Gie the electronic configuration of copper (Cu):
- 1s2, 2s2, 2p6, 3s2, 3p6, 3d10, 4s1
What is first ionisation energy?
- the energy needed to remove one mole of electrons from one mole of atoms in the gaseous state
Describe the trend in first ionisation energy down a group:
- first IE decreases down the group
- as you go down the group, atomic radius/shells/shielding increases
- nuclear attraction on the outer electron decreases
- less energy needed to remove the outer electron
Describe the trend in first ionisation energy across a period:
- General increase
- across a period, proton number increases and atomic radius decreases (shells/shielding do not change)
- nuclear attraction on the outer electron increases
- more energy needed to remove outer electron
How does first IE change between groups 2 and 3?
- small decrease in first IE
- outer electron in group 3 element is removed from the p-subshell, which is further away from the nucleus than the s-subshell
- more shielding makes it easier to remove the outer e- from the group 3 atom than expected
How does first IE change between groups 5 and 6?
- small decreases in first IE
- in the group 6 atom, the outer e- is removed from a pair in an orbital
- paired electrons have opposite spins so they repel and are easier to remove than expected
How does first IE change from the end of one period to the start of the next?
- there is a BIG DROP in first IE
- because the element at the start of the next period has an additional outer shell
- Increase in shielding and atomic radius
- so nuclear attraction on the outer e- decreases