Chapter 1 AS - Atomic Structure & The Periodic Table Flashcards
(56 cards)
What is ‘nuclear charge’ ?
- The total charge of all the protons in the nucleus.
–> It has the same value as the atomic number.
–> Increases as you go across the periodic table
What is ‘relative atomic mass’ ?
Average mass of an atom of an element, relative to 1/12ᵗʰ of the mass of an atom of carbon-12.
What is ‘relative isotopic mass’ ?
Average mass of an atom of an isotope relative to 1/12ᵗʰ of the mass of an atom of carbon-12.
What is ‘relative molecular mass’ ?
Average mass of a molecule relative to 1/12ᵗʰ of the mass of an atom of carbon-12.
Define ‘First Ionisation Energy’ .
The energy required to remove 1 mole of electrons from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions.
Define ‘Second Ionisation Energy’ .
Links to successive ionisation energy.
The energy required to remove 1 mole of electrons from each ion in 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions.
What is an ‘orbital’ ?
A region around the nucleus of an atom where electrons are most likely located and are spinning in opposite directions to each other.
What is ‘periodicity’ ?
Repeating trends in element properties with increasing atomic number.
What is ‘Hund’s Rule’ ?
When electrons fill orbitals, they first occupy them single before they pair up.
What is the ‘Pauli Exclusion Principle’ ?
A pair of electrons within the same orbital must have opposite spins.
What is the ‘Aufbau Principle’ ?
As atomic number increases, the electrons are added to orbitals in order of increasing orbital energy until all electrons are accommodated i.e. from Quantum Shell 1 and above.
Exceptions: Cr (Chromium) and Cu (Copper)
What is the relative mass of an electron?
1/1840
How can you calculate the maximum number of electrons that each shell can accommodate?
2n²
n: The number of quantum shells
e.g. 2 shells –> 2(2)² = 8 electrons
What symbol does ‘A’ represent?
Mass number
What symbol does ‘Z’ represent?
Atomic number
Describe the main stages of ‘Time of Flight (TOF): Mass Spectrometry’
1) Ionisation
2) Acceleration
3) Ion drift
4) Detection
5) Analysis
Outline ‘ionisation’ in Mass Spectrometry
- Sample is vapourised
- Sample is injected into mass spectrometer
- High voltage is passed over chamber
- Atoms are ionised as electrons are knocked off
- 1+ charged ions left in chamber
Outline ‘acceleration’ in Mass Spectrometry
The positively charged ions accelerate towards a negatively charged detection plate
Outline ‘ion drift’ in Mass Spectrometry
The ions are deflected by a magnetic field into a curved path.
The radius of their path is dependent on the charge and mass of the ion, relative to the strength of the magnetic field generated.
Outline ‘detection’ in Mass Spectrometry
- The positive ions hit the negatively charged detection plate.
- The ions gain an electron, producing a flow of charge.
- The greater the abundance, the greater the current produced.
Outline ‘analysis’ in Mass Spectrometry
These current values are then used in combination with the flight times to produce a spectra print-out with the relative abundance of each isotope displayed.
What would the mass spectrometry for a +2 ion be like? Bear in mind that +2 ions can also be produced during the ionisation stage.
- It will face greater effect from the magnetic field
- It will deflect a lot
- A curved path of a smaller radius produced by magnetic field
- The m/z is halved
How can you calculate the relative atomic mass of the sample using mass spectra?
(m/z x abundance) / Total abundance
–> Total abundance is typically 100
What does the tallest peak on a mass spectrum correspond to?
The relative molecular mass of the molecule, i.e. the molecular ion peak
(M⁺ species)
