Atomic Structure and the periodic table Flashcards
what is the mass of an electron
1/1840
atomic number (proton number) definition
number of protons in the nucleus of an atom of that element
do isotopes have the same/similar chemical properties and why
they do because isotopes of the same element all have the same arrangement and number of electrons
what determines chemical properties on an element
the arrangement and number of electrons
isotope definition
atoms of the same element with the same number of protons but a different number of neutrons
what is 1 mass unit equal to
1/12 the mass of a carbon-12 atom
relative isotopic mass definition
the mass of an atom of an isotope divided by 1/12 the mass of a carbon-12 atom
symbol for relative atomic mass
Ar
relative atomic mass definition
the weighted average mass of an atom of an element divided by 1/12 the mass of a carbon-12 atom
how to calculate r.a.m of 75% chlorine-35 and 25% chlorine-37
two isotopic forms of chlorine. 75% chlorine-35, 25% chlorine-37
sum of relative isotopic abundance (75+35)
75% chlorine-35, what is the isotopic abundance in this
75%
what technique measures abundances of different isotopes
mass spectrometry
name the four stages of mass spectrometry
ionisation, acceleration, deflection, detection
describe the ionisation (first) stage of mass spectrometry
(the sample is first vaporised, separating the atoms or molecules)
- stream of high energy electrons fired at sample
- energy from electrons strip electrons off the atoms or molecules
- positive ions formed
what is the general equation for the ionisation stage of mass spectrometry
X(g) + e- -> X+ (g) + 2e-
describe the acceleration (second) stage of mass spectrometry
- positive ions pass through an electric field
- this accelerates them into the instrument
describe the deflection (third) stage of mass spectrometry
- the ions pass through a magnetic field
- are then deflected according to their mass and charge
which type of ions will be deflected the most
those that are lighter and with a greater positive charge are deflected more
describe the detection (fourth) stage of mass spectrometry
- beam of ions passing through the machine are detected electrically by an ion detector
uses of mass spectrometry (3)
- to find mass of molecule
- carbon dating
- to find what is in a molecule
what is the relative molecular mass
the average mass of a molecule of that element or compound divided by 1/12 the mass of a carbon-12 atom
define the relative formula mass
average mass of a formula unit divided by 1/12 the mass of a carbon-12 atom
what is the name of the peak with the highest m/z on the mass spectrum graph and what does it show
- molecular ion peak
- relative formula mass/molecular mass of the molecule
why are there some lines to the left of the molecular ion peak on a mass spectrum graph
they are due to fragment ions which arise from some molecules breaking down
