Atomic structure Flashcards
What is the relative mass of an electron ?
1/1840
A and Z are used to represent what features of an element?
A = mass number
Z = number of protons
Define relative atomic mass
The mean mass of an atom of an element divided (relative) by 1/12th of the mean mass of an atom of the carbon-12 isotope.
Why will neutral isotopes react the same chemically?
Because their proton number and electron configuration is the same so the sharing and transfer of elections is unaffected.
Describe the 5 steps of Time Of Flight Mass Spectrometry
- IONISATION = sample of element is vaporised and injected into mass spectrometer were high voltage is passed over chamber to remove electrons (get ionised). Leaving +1 charged ions in the chamber.
- ACCELERATION = positively charged ions are accelerated towards negatively charged detection plate
- ION DRIFT = ions are deflected by a magnetic filled into a curved path. The radius of their path is dependent on the charge and mass of the ion.
- DETECTION = when positive ions hit the negatively charged detection plate, they hon an electron producing a flow of charge. The greater the abundance, the greater the current made.
- ANALYSIS = current values are then used in combination with the flight times to produce a spectra print-out with the relative abundance of each isotope displayed.
How is Ar calculated using the spectra?
Ar =( m/z x abundance ) / total abundance
How do electrons in atoms pair in orbitals to ensure stability?
electrons pair up with the opposite spin. Electrons in the same orbital must have opposite spin.
What may happen to electrons in their orbitals if they are unpaired making the orbitals unbalanced?
Due to a natural repulsion being formed between the electrons making the atom very unstable, they take on a different arrangement to improve stability. E.g 3p4 —> 3p3 4s1
Define ionisation energy
The minimum energy required to remove one mole of electrons from one mole of atoms in a gaseous state. (kJmol-1)
How do successive ionisation energies change as more electrons are removed?
More energy is required to pull electrons off as electrostatic force of attraction between the positive nucleus and negative outer electron increases. More energy is hence needed to overcome this attraction so ionisation energy increases.
How does ionisation energy change along a period?
1st ionisation energy increases due to a decreasing atomic radius and greater electrostatic forces of attraction
How does ionisation energy change down a group?
1st ionisation energy decreases due to an increasing atomic radius and shielding which reduces the effect of the electrostatic forces of attraction
What evidence supports atomic orbital theory?
When successive ionisation energies are plotted on a graph, a sudden large increase indicates a change in energy level as the electron is being removed from an orbital closer to the nucleus so more energy is required to do so.
Why is the 1st ionisation energy of aluminium lower than expected?
It has a single pair of electrons with opposite spin which holds natural repulsion and reduced the amount of energy needed to be put in to remove the outer electron.
