Atomic Structure Flashcards
What is the definition of first ionisation energy?
The amount of enthalpy needed to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous ions.
What is the definition of mean molecular/atomic mass?
The mean mass of a molecule/atom relative to one 12th of a carbon – 12 atom.
What is the definition of molecular formula.
The amount of atoms of each element in a molecule.
What determines the chemical properties of a particle.
The electron structure
Across period 3 the first ionisation energies decrease across the period. What are the two exceptions to this and why?
Magnesium to aluminium because Al has its highest energy electron in a p sub-shell and Mg has its highest energy electron in an s sub-shell and the p sub-shell is higher in energy compared to s and is on average further from the nucleus and shielded from s.
Phosphorous to sulfur because in P the electrons in the p orbital are unpaired but in S an electron pair exists in a p orbital and repulsion between these electrons reduces the energy required to remove an electron from S.
