Atomic Structure Flashcards
What’s the symbol for atomic number?
Z
What’s the symbol for atomic mass?
A
How do isotopes differ in chemical properties?
They don’t
For ToF mass spec of atoms, when there are small peaks at lower m/z; why are they there, why is that their m/z value and how big are there peaks and why?
These are 2+ ions of the element in question. There m/z is just half the m/z of their normal isotopes and they have very small peaks because more energy is needed to remove the second electron
After 3d, state the order of subshell filling
4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p, 8s
What’s the ‘valence shell’?
The incomplete outermost shell of an atom
What’s the name for ‘the incomplete outermost shell of an atom’?
The valence shell
What’s the shell of an atom?
The area around the nucleus where electrons orbit
What’s the name for ‘the area around the nucleus where electrons orbit’?
The shell of an atom
What’s a subshell of an atom?
Shells which are divided into smaller shells; s, p, d & f, and are made of orbitals
What’s the name for ‘shells which are divided into smaller shells’?
Subshells
What’s an orbital?
Regions around the nucleus that can hold up to 2 electrons, making up subshells
What’s the name for ‘regions around the nucleus that can hold up to 2 electrons’?
Orbitals
What’s electron spin?
A quantum mechanical property of electrons. In an electron pair inside an orbital, if one spins upwards the other must spin downwards, they can’t spin in the same direction
What’s the name for the quantum mechanical property of electrons that says that in an electron pair inside an orbital, if one spins upwards the other must spin downwards, they can’t spin in the same direction?
Electron spin
Suggest what might cause the relative atomic mass of a sample produced from Mass Spec to be different from the relative atomic mass given in the Periodic Table
Other isotopes present / some isotopes absent / different abundances of
isotopes
Write an equation for the reaction that occurs when an ion (M+) hits the detector in Mass Spec
M+ + e(−) -> M
Ignore state symbols
Allow M^2+ + 2e(−) -> M
State the m / z value of the ion that produces the biggest current at the detector when the spectrum in the graph is recorded.
Most abundant ion
Predict whether the atomic radius of Te-124 is larger than, smaller than or the same as the atomic radius of Te-130. Explain your answer.
Same because each isotope has the same number of protons / same nuclear charge and
same number of electrons / electronic configuration
Ignore more neutrons in Te-130
Explain why it is necessary to ionise molecules when measuring their mass in a TOF mass spectrometer
- Ions, not molecules, will interact with and be accelerated by an electric field
- Only ions will create a current when hitting the detector
In a mass spectrometer, the isotopes of an element are separated. Two measurements for each isotope are recorded on the mass spectrum. State the two measurements that are recorded for each isotope.
- m/z ratio
- Relative Abundance
Define the term relative atomic mass
Average mass of 1 atom of an element compared to 1/12th mass of one atom of 12C
When given a mass spectrum with peaks of different abundances at different m/z ratios, which one of the isotopes is deflected the most in the magnetic field of a mass spectrometer? Why?
Pick whichever ion has the lowest m/z ratio because it has the lowest m/z ratio
In a mass spectrometer, the relative abundance of each isotope is proportional to the current generated by that isotope at the detector. Explain how this current is generated
Electron(s) transferred / flow at the detector from detector / plate to the (+) ion
Do not allow from a charged plate
A sample of ethanedioic acid was treated with an excess of an unknown alcohol in the presence of a strong acid catalyst. The products of the reaction were separated and analysed in a time of flight (TOF) mass spectrometer. Two peaks were observed at m / z = 104 and 118. Identify the species responsible for the two peaks
[CH3OCOCOOH]+ and [CH3OCOCOOCH3]+
Allow names, do not allow molecular formula
You’re given 2 species and their m/z. Outline how the TOF mass spectrometer is able to separate these two species to
give two peaks
Positive ions are accelerated by an electric field to a constant kinetic energy. The positive ions with lower m/z have the same kinetic energy as those with
higher m/z yet moves faster. Therefore, ions with lower m/z arrive at the detector first
If the mass of a proton, neutron and electron is 1.6725 x 10^-24 g, 1.6748 x 10^-24 g and 0.0009 x 10^-24 g respectively, what’s the mass of a H atom?
1.6734 × 10^−24 g
