topic 1: Atom Structure

Question 1

what is relative isotopic mass?

Answer 1

refers to the mass of an atom of an isotope relative to carbon-12, which has an atomic mass of 12

Question 2

how to calculate RAM from isotopes?

Answer 2

Ar: (mass of I1 x % abundance 1) + (mass of I2 x % abundance of I2) / total %

Question 3

what is mass spectrometry used for?

Answer 3

to find the relative mass of elements and compounds

Question 4

what happens in the first stage of ionisation? for low Mr compounds? For high Mr compounds?

Answer 4

low Mr compounds: high energy electrons are fired at the sample from an electron gun, knocking off one electron from each atom/molecule to form a 1+ ion
high Mr compounds: electronspray ionisation: sample is dissolved in a volatile solvent (methanol/water) and injected through a fine hypodermic needle as a fine spray into a vacuum in the ionisation chamber
a very high voltage is applied to the end of the need,e where the spray emerges
the particles gain a proton and become ions as a fine mist
the solvent evaporates leaving 1+ ions

Question 5

what happens in the second stage of mass spectrometry: acceleration

Answer 5

the ions are accelerated using an electric field so that all the ions have the same kinetic energy