A Level Chemistry - Unit 1
What are the masses of Protons, Neutrons and Electrons?
Protons - 1, Neutrons - 1 and Electrons - 0 (1/1840)
What are the charges of Protons, Neutrons and Electrons?
Protons - +, Neutrons - no charge and Electrons - -
Whats the Mass Number?
The number of protons and neutrons combined together in the element.
Whats the Atomic Number?
The number of protons and electrons in the element.
Whats an Isotope?
Atoms with the same atomic numbers but different mass numbers, aka a different number of neutrons.
Whats an example of an Isotope?
Carbon or Chlorine : C12, C16 and C14. Cl35 and Cl37.
How many electrons can all the shell levels hold?
1 - 2 electrons, 2 - 8 electrons, 3 - 18 electrons and 4 - 32 electrons.
Whats a Time of Flight Mass Spectrometer?
It's a machine that can either measure the relative atomic mass of an atom or the relative molecular mass of a substance.
How can a Mass Spectrometer be used?
It can be used in places like law enforcement to detect isotopes that can detect either illegal drugs or harmless substances, for example different variations of Carbon.
How does a Mass Spectrometer work?
It works by accelerating an ionised sample and calculating mass per charge based on how long each 'object' is in flight for. Every 'object' recieves an equal force according to Newtons 2nd law - the 'objects' acceleration should be inversely proportional to their mass.
How is the sample ionised?
By bombarding it with electrons, this causes fragmentation to form smaller groups of atoms, as ions have a +1 charge, and electrons a -1, it knocks an electron out of a shell and charge per mass is just considered mass.
What is a Drift Reigon?
It's a vacuum area, that ions are accelerated through via an electromagnetic field.
Why does a Time of Flight Mass Spectrometer need a vacuum?
As it is important that any ions produced in the ionisation chamber do not have any effect on surrounding air molecules when passing throigh the machine as this could drastically change the results.
What's the Ionisation Process?
The vaporised sample passes through the chamber where the electrically heated metal coil gives off electrons, which are then attracted to a positively charged plate in an electron trap.
What's a Repeller?
Another metal plate that carrys a slight positive charge to attract the ions when exiting the ionising chamber.
What are the two basic types of Mass Spectrometry?
High and Low Resolution.
What's High Resolution?
It detects relative atomic mass upto 5 decimal places.
What's Low Resolution?
It detects relative atomic mass to the nearest whole number.
Which is more common between High and Low Resolution?
Low Resolution.
How to calculate Relative Atomic Mass?
Chlorine as an example : Cl35 = 75% and Cl37 = 25% - (75 x 35) + (25 x 37) / 100 = 35.5.