Atomic Structure Flashcards
What was the plum pudding model?
A sphere of positive charge with small negative charges distributed evenly within it
What was the electron shell model?
A small dense central nucleus orbited by electrons in shells
Define relative atomic mass
The mean mass of an atom of an element relative to 1/12 the mass of an atom of carbon-12
What are isotopes?
Atoms of the same element that have a different number of neutrons
Do isotopes have the same chemical properties and why?
Yes because their electron configuration is the same
Do isotopes have the same physical properties and why?
No because they have different masses
What is an ion?
An atom that has lost or gained electrons so has an overall charge
What is mass spectrometry?
An analytical technique used to identify different isotopes and find the Ar of an element
What is TOF mass spectrometry?
A type of mass spectrometry that records the time it takes for ions to reach a detector
What is produced by TOF mass spectrometry?
A spectra that shows each isotope that is present
What are the 5 stages of TOF mass spectrometry?
Ionisation, acceleration, ion drift, detection, analysis
What are the 2 types of TOF ionisation?
Electron impact and electrospray
How does electron impact ionisation work?
The sample is bombarded with high energy electrons, causing it to lose an electron
How does electrospray ionisation work?
Sample dissolved in volatile solvent, injected through high voltage needle, to gain a proton
Why do molecules need to be ionised for TOF mass spectrometry?
Molecules won’t be accelerated by an electric field or create a current when hitting the detector
What happens during TOF acceleration?
Ions are accelerated to the same kinetic energy
Why are ions accelerated to the same kinetic energy for TOF mass sepctrometry?
Kinetic energy = 1/2mv2 so velocity is determined by mass
What happens during TOF ion drift?
The ions separate based on their different velocities
What happens during TOF ion detection?
The positively charged ions hit the detector and cause a small electric current
What happens during TOF data analysis?
The ions’ flight times are recorded as a mass spectrum
What is a TOF mass spectrum?
A plot of relative abundance against mass to charge ratio (m/z)
What does a mass spectrometer provide?
Accurate information about relative isotopic mass and the relative abundance of isotopes
What can mass spectrometry be used to do?
Identify elements and determine relative atomic mass
Which elements have unusual electron configurations?
Chromium and copper
How is the electron configuration of chromium unusual and why?
It’s 3d5 4s1 instead of 3d4 4s2 because the symmetry around the nucleus makes it more stable
How is the electron configuration of copper unusual and why?
It’s 3d10 4s1 instead of 3d9 4s2 because the symmetry around the nucleus makes it more stable
What is first ionisation energy?
The energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions
How do the successive ionisation energies in period 3 give evidence for electron shells and sub-shells?
Aluminium has a lower than expected ionisation energy because it is in a sub-shell further from the nucleus
How do the successive ionisation energies in group 2 give evidence for electron shells and sub-shells?
Ionisation energy decreases down the group due to additional electron shells
