Atomic Structure and the Periodic Table Flashcards
What is an isotope?
An isotope can be defined as an atom of an element with a different number of neutrons.
What remains the same about all isotopes of the same element?
They all have the same number of protons (making it the same element) and the same number of electrons.
What properties of isotopes remain the same and why?
Their chemical properties remain the same due to them all having the same number of electrons.
What properties of isotopes change and why?
Their physical properties change due to them having different number of neutrons. For example, carbon-14 is radioactive but no other carbon isotopes are.
Relative atomic mass is what?
The weighted mean mass of an atom of an element relative to 1/12th of the mass of an atom of carbon-12.
Weighted mean mass takes into account what?
The percentage abundance of each isotope and the relative isotopic mass of each isotope.
Relative isotopic mass means what?
The mass of an isotope relative to 1/12th of the mass of an atom of carbon-12.
Cl-35 has abundance of 75.78%.
Cl-37 has abundance of 24.22%.
What is the RAM of Cl.
(75.78x35)/100 + (24.22x37)/100
35.4844 = 35.5 (1dp)
To calculate the relative molecular mass we do what?
Add together the relative atomic masses of each of the atoms in the molecule.
To calculate the relative formula mass we do what?
Exactly the same as relative molecular mass (add together the relative atomic masses of each of the atoms), just on larger molecules.
What instrument can we use to measure percentage abundances?
A mss spectrometer.
A mass spectrometer measures what?
The masses of atoms and molecules (as well as fragments that make the molecule).
Mass spectra is what?
The graph/results at the end of using the mass spectrometer.
What is the molecular ion peak (M+)?
The strongest peak to the right on a mass spectra.
The M+1 is what?
A result of other isotopes in the sample and appears to the right of the M+.
What is the order for mass spectrometry?
Vapourisation Ionisation Acceleration Deflection Detection
Why are samples vapourised for mass spec?
The sample needs to be gaseous for mass spec to work.
Why are particles ionised for mass spec?
The particles need to be positively charged for them to be accelerated. They are subjected to a beam of high energy electrons.
What happens in the ioniser in mass spec?
The ioniser is a vacuum and the sample is subjected to high energy electrons to ionise the sample. The electrons remove electrons from the sample to form positive ions.
What happens in the mass analyser in mass spec?
Ions are accelerated in a negative electric field then a magnetic field deflects the ions.
What does the detector do in mass spec?
Detects deflected ions, contains an electron multiplier and an amplifier to detect the deflection on ions by the magnetic field.
What do different rates of deflection in mass spec show?
Different rates of deflection by the magnetic field shows different atomic masses as more massive isotopes are deflected less by the magnetic field, whereas less massive isotopes are deflected more.
Electrons exist in what kind of shells?
Quantum shells.
The first quantum shell is where relative to the nucleus?
Closest to the nucleus.
Electrons that exist in the first quantum level have the lowest what?
Energy level.