Atomic Structure Flashcards
Why do ionisation energies increase across a period?
- Nuclear charge increases, while there are negligible increase in shielding effect as electrons are removed from the same shell. Thus, effective nuclear charge increases. Atomic radius also decreases across the period. More energy is required to remove the valance electrons that are increasingly more attracted by the positive nucleus.
Why is there a drop in ionisation energy from Be to B
the 2p electron from B has a higher energy than the 2s electron to be removed from Be.
Why is there a drop in ionisation energy from N to O
Coulombic repulsion between the paired 2p electrons in O makes it easier to remove one of the paired 2p electrons than an unpaired 2p electron.
Why do ionisation energies decrease down the group?
Down the group, atomic radius increases, shielding effect increases due to the increase in the number of principle quantum shells, which cancels out the increase in nuclear charge. Less energy is required to remove the valence electrons as the valence electrons become increasingly less attracted by the positive nucleus.
Why is the 2nd ionisation energy higher than the first ionisation energy?
The 1st IE involved removing electrons from a neutral atom while the 2nd IE involves removing electron from a positively charged ion. Therefore more energy is required to remove the second electron which experiences greater attraction to the nucleus of the positively charged ion.
Explain how the trends of the 2nd ionisation energy is related to the trend in the 1st ionisation energy.
Isoelectric species: Na+ and Ne
Mg+ and Na+
P+ and Si
Removing the first energy from Ne is similar to removing the 2nd electron from Na, both involved the removal of an electron from a completely filled principal quantum shell. Thus the trends for 1st and 2nd IE are alike, except that trend has shifted 1 element to the right for 2nd IE
