Atomic Structure Flashcards

Active recall practice for basic particles, TOF mass spectrometry, configurations, and ionisation trends.

Fundamental Particles & Isotopes: read all 3 questions and answers

Define isotope.
Atoms of the same element with the same number of protons but different numbers of neutrons.
What determines the chemical properties of isotopes?
The electronic configuration / number of electrons in the outer shell, which is identical for isotopes of the same element.
Why do isotopes have different physical properties?
Because they have different masses, affecting properties like density, boiling point, and rate of diffusion.

Time of Flight (TOF) Mass Spectrometry: read all 6 questions and answers

Describe electron impact ionisation in a TOF mass spectrometer.
The sample is vaporised and high energy electrons from an electron gun are fired at it, knocking off one electron to form a 1+ ion.
Describe electrospray ionisation in a TOF mass spectrometer.
The sample is dissolved in a polar solvent and injected through a fine needle connected to a high voltage supply, gaining a proton (H⁺) to form MH⁺ ions.
What is the main purpose of the acceleration stage in TOF mass spectrometry?
To give all ions the same kinetic energy, so their velocity (and drift time) depends only on their mass.
State the relationship between time of flight (\(t\)) and mass (\(m\)) of an ion in a TOF mass spectrometer.
Time of flight is directly proportional to the square root of the mass of the ion (since \(t = d \times \sqrt{\frac{m}{2\text{KE}}}\)).
How are ions detected in a TOF mass spectrometer?
The positive ions hit a negatively charged detector plate, gain an electron, and generate an electrical current.
How is the abundance of an isotope determined from the detector current in a mass spectrometer?
The size of the current generated is directly proportional to the abundance of that isotope.

Electron Configuration: read all 5 questions and answers

State the maximum number of electrons that can occupy s, p, d, and f sub-shells.
s holds 2; p holds 6; d holds 10; f holds 14.
Define an orbital.
A region of space around the nucleus where there is a high probability of finding up to two electrons with opposite spins.
Write the full electron configuration of a Chromium (Cr) atom.
\(1s^2 2s^2 2p^6 3s^2 3p^6 3d^5 4s^1\).
Why is Chromium's configuration anomalous?
It is more stable to have a half-filled d sub-shell (\(3d^5 4s^1\)) due to symmetrical electron distribution and lower electron-electron repulsion.
Write the full electron configuration of an Fe³⁺ ion.
\(1s^2 2s^2 2p^6 3s^2 3p^6 3d^5\) (the 4s electrons are lost before the 3d electrons).

Ionisation Energies: read all 5 questions and answers

Define first ionisation energy.
The energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions.
Write the equation, including state symbols, for the second ionisation energy of magnesium.
Mg⁺(g) → Mg²⁺(g) + e⁻
Explain the general trend in first ionisation energy across Period 3.
It increases, because nuclear charge increases and shielding remains constant, so the electrostatic attraction between the nucleus and outer electrons increases.
Explain why the first ionisation energy of sulfur is lower than that of phosphorus.
Sulfur has paired electrons in a 3p orbital. The repulsion between these paired electrons makes the outer electron easier to remove.
Explain why the first ionisation energy of aluminium is lower than that of magnesium.
Aluminium's outer electron is in a 3p sub-shell, which is higher in energy and further from the nucleus than magnesium's 3s outer electron, and is shielded by the 3s electrons.