3.1.1 Atomic structure Flashcards
Isotopes
Atoms of the same element but with different number of neutrons.
What can mass spectrometry be used for?
- find the abundance and mass of each isotope in an element
2. find the relative molecular mass of substances made of molecules
Two types of ionisation
Electron impact and electrospray ionisation
Electron impact
High energy electrons are fired from a hot cathode at the sample. This knocks off one electron and forms a positive ions
Equation for electron impact
X(g) ￫ X+(g) + e-
Electrospray ionisation
Sample dissolved in volatile solution and injected through a fine hypodermic needle giving a fine mist. The tip of the needle has a high voltage and each atom gains a proton as it leaves the needle.
Forming a positive ion
When is electrospray ionisation used?
On molecules with a high Mr value as using electron impact can cause fragmentation
What type of molecules travel faster in acceleration?
lighter particles travel faster
How many electrons can electron orbital hold?
2
What are orbitals
Regions of space that electrons are most likely to be in
Aufbau principle
Electrons enter the lowest orbital available
Hunds rule
Electrons prefer to enter orbitals on their own, they only pair up when no empty orbitals of the same energy are available.
4s and 3d orbital?
The 4s orbital fills up before the 3d orbital. However, when losing electrons, electrons are lost from the 4s before the 3d.
First ionisation energy
The energy required to remove one mole of electrons from one mole of gaseous atoms to provide one mole of gaseuous single charged ions.
Ionisation energy is affected by…
- Atomic radius
- number of protons
- shielding
