Ionisation Energy

Question 1

Comparing Rutherford model and experiment

Answer 1

• Fired He2+ ions at a sheet of gold foil, when the hit the foil he concluded that most of the atom was empty space. a very small number of the ions were detected in the Centre suggesting that the atom must have a small positive nucleus.
• Bohr model: Small positive nucleus , the electrons surround the nucleus in energy shells. Nucleus also contains neutrons

Question 2

Ionisation energy definition and example

Answer 2

Amount of energy needed to remove one mole of electrons from a mole of atoms in a gas state.
First IE of K: K(g) –> K+(g) + e-

Question 3

Factors that influence IE

Answer 3

• Nuclear charge, number of protons- more protons, stronger attraction to nucleus, requires more energy
• Distance from the nucleus- Electron closer to nucleus, stronger attraction, more energy required.
• Shielding- Electron on shell further from the nucleus- more shielding, weaker attraction. Less energy to remove.

Question 4

Trend in IE across the group: why is second IE high then first?

Answer 4

Why- the attraction between the electron and protons becomes stronger as there a less electrons being attracted by the same number of protons.- 2nd electron is removed from an ion that already has a positive charge
Trends: general increase, same shielding, more protons.
Deviations P2: Electron to be removed from Be is from a 2s sub-shell, from B it is in a 2p sub-shell. 2p is higher, less energy required to remove.
Electron to be removed from N is unpaired, O is paired. Electron pairs repel, requires less energy to remove.
P3: electron to be removed from Mg is 3s, Al is 3p. 3p= higher sub-shell, requires less energy to remove.
Electron to be removed from P is unpaired, S is paired. Electron pairs repel, Sulfur has lower IE due to less energy being required to move

Question 5

Change in atom size

Answer 5

factors affecting- same shielding, more protons so greater nuclear attraction on outer electrons- smaller ion
more shielding, further from the nucleus, weaker nuclear attraction, more shielding.

Question 6

Electron configuration

Answer 6

Cr: 1s2 2s2 2p6 3s2 3p6 4s2 3d9
Cu: 1s2 2s2 2p6 3s2 3p6 4s1 3d10

Question 7

trends in IE down the group, atomic size trend across the period

Answer 7

Atomic radius increases, the number of shells increases so amount of shielding increases.
Atomic radius gets smaller, nuclear charge increases, greater attraction between electrons and nucleus, shielding remains the same.

Question 8

TOF spectrum

Answer 8

Vacuum to prevent particles colliding with air.
acceleration: positive ions attracted to a negatively charged plate and accelerate towards it. Once accelerated all have the same KE.
Ion Drift- particles separate based on their masses.
Detection: generates a current once hits the detector- generating a current proportional to the number type of each ion.

Question 9

Why are the sample particles ionised?

Answer 9

So they can be accelerated towards the negatively charged pate and generate a current once hit the detector

Question 10

How is the ion accelerated? and how are they separated? How are they detected?

Answer 10

Positive ions are attracted to negatively charged plate, all have the same kinetic energy.
Ions travelling at higher speeds reach the detector first.
detection: Each ion hits the detector, gains an electron, generated a current which is proportional to abundance of ion.