1.1 Atomic Structure (AS) Flashcards
Describe the Plum Pludding model
J.J Thompson
- Sphere of positive charge
- small negative charges distributed evenly throughout it
Describe the electron shell model
- Small, dense central nucleus
- surrounded by orbiting electrons in electron shells
discovered by rutherford
Define Relative atomic mass
Mean mass of an atom of an element, divided by one twelfth of the mean mass of an atom of the carbon-12 isotope
Define an isotope
- Atoms of the same element
- Same Atomic Number
- Different Mass number
What do isotopes have different between each other
Different physical properties
How are ions formed
- When an atom loses / gains an electron
- no longer neutral
- will have an overall charge
What is mass spec used for
- Analytical technique
- to identify diff isotopes
- to find overall atomic mass of element
How does TOF mass spec work
- Records time it takes for iones of each isotope to reach a detector
- Produces spectra to show each present isotope
Name the five stages of TOF mass spec
- Ionisation
- Acceleration
- Ion Drift
- Detection
- Analysis
Describe and Explain how TOF Mass spec works
- Ionisation
Sample is vaporised + injected into spectrometer where high voltage passed over chamber. This removes 1 electron, ionising - Acceleration
Ions are accelerated towards negatively charged detection plate - Ion Drift
Ions are deflected by a magnetic field into a curved path. - Detection
Ions hit the plate, gaining electron, producing flow of charge. Greater abundance = greater charge - Analysis
Current values used in combination with flght times to produce spectra, with relative abundance of each isotope
What does the radius of ions’ path during ion drift in TOF mass spec dependant on?
Charge and Mass of the ion
What happens to the m/z ratio, when a 2+ ion is produced
The m/z ratio is halved, and can be seen on the spectra as a trace at half the expected m/z value
How many electrons can each orbital hold
- S-orbital = 2 electrons
- P-orbital = 6 electrons
- D-orbital = 10 electrons
How does energy change from orbitals s-d
Energy increases across orbitals s-d, meaning orbitals filled in this order.
Explain electron spin pairing
- electrons pair up with oppsoite spin
- to make the atom stable
- atoms in same orbital must have opposite spin
What does electron spins that are unpaired produced
Natural repulsion
Explain natural repulsion
- Electron spins are unpaired and unbalanced
- atom is very unstable
- electrons may take on a diff arrangement to improve stability
Define ionisation energy
The minimum energy required to remove one mole of electrons from one mole of stoms in a gaseous state. it is measured in kJmol-1
Explain successive ionisation energies
- Further electrons removed
- requires more energy to remove
- electrostatic attraction increases as atomic radius decreases
- eneergy needed to overcome this attraction
- ionisation energy increases
Explain the trend in first ionisation energy along a period
- Ie increases
- decreasing atomic radius
- greater electrostatic force of attraction
Explain the trend in first ionisation energy down a group
- Ie decreases
- increasing atomic radius
- shielding
- reduces electrostatic forces of attraction
How does Ionisation energy change as you take it from the next orbital
- sudden increase in Ie
- electron removed from orbital closer to nucleus
- more electrostatic attraction
- therefore more energy requuired
Explain the first ionisation energy of aluminium
(it drops)
- lower than expected
- single pair of electrons with opposite spin
- natural repulsion
- easier removal
- reduces the amount of energy needed to remove
