Chapter 2 Flashcards
What is the atomic number?
Number of protons IN THE NUCLEUS (also number of electrons)
What is the mass number?
Number of protons AND neutrons in the nucleus
What is an isotope?
Atoms of the same element with different numbers of neutrons BUT the same number of protons and electrons
What is an ion?
Where an atom has lost or gained an electron
What is relative isotopic mass?
The mass of an isotope compared with 1/12th of the mass of an atom of Carbon-12 (mass no. 12)
What is relative atomic mass?
The WEIGHTED MEAN mass of an atom compared with 1/12th of the mass of an atom of Carbon-12
What does Ar take into account?
The percentage abundance of each isotope & the relative isotopic mass of each isotope.
How do we figure out the percentage abundance & relative isotopic mass?
Through mass spectroscopy
What is the first stage of a TIME OF FLIGHT mass spectrometer?
To vaporise the sample and then ionise into a SINGLE POSITIVE ION
Why do we ionise the sample into a single positive?
To make the mass to charge ratio (M/Z) equal to the masses of the isotopes (as mass/1 will always = the same)
How do we ionise the sample? What is the ionic equation of this?
By blasting it with a high energy beam of electrons (which knocks 1 electron off the shell). X(g) + e- –> X+(g) + e-
+ e-
What is the second step of mass spectroscopy?
The ions are accelerated to the same kinetic energy, by an electrical field (neg = opps attract) however they are going to different velocities as shown by the equation.
What are the results of mass spectroscopy?
The lowest masses always arrive first due to the kinetic energy equation (dividing by a smaller number = a bigger number)
What do you get after this?
A computer analyses the results and creates a mass spectrum.
How do you calculate the Ar with a mass spectrum?
Ar = (abundance x rim) + (abundance x rim) etc/total perc abundance
