Atomic Structure

Question 1

Explain factors influencing ionisation energy

Answer 1

1) Nuclear charge
-higher charge/more protons =stronger attraction between the nucleus and the outer electron.More energy needed to remove the outer electron
-lower charge /less protons =weaker attraction between the nucleus and the outer electron.Less energy needed to remove the outer electron
2)Distance from the nucleus
-closer to the nucleus = stronger attraction.More energy needed to remove the outer electron
-further away from the nucleus = weaker the attraction so less energy needed to remove the outer electron
3)Shielding
-more shells=more shielding, this blocks the attraction making it weaker
-less shielding =stronger attraction so more energy needed to remove the outer electron

Question 2

Why is second ionisation energy of B higher than the first

Answer 2

Second electron is removed from an ion that already has a positive charge

Question 3

Relative mass of a proton

Answer 3

1

Question 4

Relative charge of a proton

Answer 4

1+

Question 5

Relative mass of a Neutron

Answer 5

1

Question 6

Relative charge of a neutron

Answer 6

0

Question 7

Relative mass of an electron

Answer 7

1/1840

Question 8

Relative charge of an electron

Answer 8

1-

Question 9

Isotopes

Answer 9

Atoms with the same number of protons but a different number of neutrons.They have the same chemical properties due to the same electronic configuration

Question 10

Ionisation energy

Answer 10

About of energy to remove a mole of electrons from a mole of atoms in the gaseous state

Question 11

Electronic configuration

Answer 11

1s2 2s2 2p6 3s2 3p6 4s2 3d10

Question 12

Trend in ionisation energies across period 2

Answer 12

• general trend : increases as there is a greater nuclear charge , same amount of shielding, attraction on outer electron gets stronger
  -first electron removed from Be is from a 2s sub-level whereas in B it’s removed from a 2p sub-level.2s sublevel is lower in energy than 2p therefore less energy needed to remove electron from B
• first electron removed from N is removed from an 2p orbital and is unpaired, first electron removed from O is in a 2p orbital and is paired.
  O has a lower ionisation energy due to electron pair repulsion so less energy needed to remove an electron from O

Question 13

Ionisation energies across period 3

Answer 13

-general trend: increases as there is greater nuclear charge, same shielding so a greater attraction between the nucleus and the outer electron
-first electron removed from mg is in a 3s sub level and the first electron removed from al is from 3p sublevel
3s sub level is lower in energy than 3p so less energy needed to remove the electron in Al
-first electron removed from P is a 3p sublevel and is unpaired whereas the electron removed from S is in a 30 sublevel but it paired.S has a lower IE energy due to electron pair repulsion therefore less energy needed to remove an electron from S

Question 14

How does ionisation energy change down a group

Answer 14

-Atoms get bigger as they have more shielding
-There is a weaker attraction between a nucleus and the outer electron
-Ie decreases down a group

Question 15

State and explain the trend in atomic radius down a group

Answer 15

-atomic radius increases as shielding increases

Question 16

Why does atomic radius gets smaller from right to left across a period

Answer 16

-atoms have more protons
-shielding is the same
-nuclear attraction on outer electron gets stronger

Question 17

What two factors does mass spectrometer measure

Answer 17

-relative abundance
-mass/charge ratio(m/z)

Question 18

Process of mass spectrometer

Answer 18

1)Vaccum
Entire machine is a vacuum inside to prevent the particles being tested colliding with molecules from the air
2) ionisation
Two methods : electron impact or electrospray( in both methods the sample particles gain a positive charge )
3)Acceleration
Positive ions are attracted to a negatively charged plate( high m/z ratio will accelerate lower to lower speeds )
Once accelerated all the ions have the same kinetic energy
4) Ion drift
Some ions will pass through a hole in negatively charged plate.Forming a beam of particles and travel along the flight tube towards the detector. Due to particles travelling at different speeds they drift apart as the slower particles can’t keep up with the faster ones
5) Detection
Different m/z ratios arrive at the detector at different times due to different velocities
They generate a current which is proportional to the number of each type of ion
6) data analysis
Signal from the detector is passed to a computer which generates a mass spectrum

Question 19

Why are the sample particles ionised in mass spectrometer

Answer 19

-So they can be accelerated towards the negatively charged plate
- so they can generate a current when they hit the detector

Question 20

How is the ion accelerated in a mass spectrometer

Answer 20

-Positive ions are attracted to the negatively charged plate
-All ions have the same kinetic energy

Question 21

How are ions separated in the flight tube in mass spectrometer

Answer 21

Ions travelling at higher speeds ( small m/z) move ahead of those travelling more slowly

Question 22

How are ions detected in mass spectrometer

Answer 22

-each ions hits the detector
- ions gains an electron
- generates a current which is proportional to the abundance of the ion

Question 23

Electron impact ionisation

Answer 23

Sample is vaporised and then high energy electrons are fired at it which come from an electron gun witch is a hot wire filament. It knocks off one electron forming a 1+ ion