Ionisation Energies Flashcards
(14 cards)
What is ionisation energy?
Ionisation energy measures how easily an atom loses electrons to form positive ions.
What is 1st ionisation energy?
The first ionisation energy is the energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1 plus ions.
What are the factors which affect ionisation energy?
Atomic Radius
Nuclear Charge
Electron Shielding
How does atomic radius affect ionisation energy?
The greater the distance between the nucleus and the outer electrons, the less the nuclear attraction. The forces of attraction falls off sharply with increasing distance.
If the atomic radius is quite big, is the ionisation energy high or low?
Low as the greater the distance between the nucleus and the outer electrons, the less the nuclear attraction.
How does Nuclear charge affect ionisation energy?
The more protons there are in the nucleus of an atom, the greater the attraction between the nucleus and the outer electrons.
If the nuclear charge is high, due to lots of protons, is the ionisation energy high or low?
High as the more protons in an atom the more attraction between the nucleus and the outer electrons.
How does electron shielding affect ionisation energy?
Electrons are negatively charges so inner electrons(1st shell) repel outer electrons(outer shell). Therefore this repulsion, called the shielding effect, reduces the attraction between the nucleus and the outer electrons.
If there is high electron shielding, due to lots of shells, is the ionisation energy high or low.
Low as the more electron shells an atom has, the more inner electrons there are to shield the outer electrons from the attraction of the nucleus. Therefore attraction between nucleus and outer electrons decrease.
How can you determine how many ionisation energies an element has?
An element has as many ionisation energies as electrons.
For example, helium has 2 electrons so it has 2 ionisation energies.
Would the 2nd ionisation energy of helium be the same as the 1st ionisation energy of helium?
No it would be higher. This is due to there being two protons in helium attracting 2 electrons. Once the 1st electron is lost the single electron is pulled closer to the helium nucleus. As the nuclear attraction on the remaining electron increases and more ionisation energy will be needed to remove this second electron.
What is the definition of the second ionisation energy?
The second ionisation energy is the energy required to remove one electron from each ion in one mole of gaseous 1 plus ions of an element to form one mole of gaseous 2 plus ions.
Is the 1st ionisation energy of boron higher than the 1st ionisation energy of beryllium?
No it is less. This is because the 2p sub shell in boron has a higher energy than the 2s sub shell in beryllium. Therefore the 2p electron is easier to remove in boron than the 2s electrons in beryllium. So the 1st ionisation energy of boron is less than the 1st ionisation energy of beryllium.
Is the 1st ionisation energy of nitrogen higher than the 1st ionisation energy of oxygen?
Yes it is. Both nitrogen and oxygens highest energy electrons are in a 2p sub shell. In oxygen the pair of electrons make it easier to remove one as the electrons repel each other. While in nitrogen the electrons are not paired. Therefore, the 1st ionisation energy of Nitrogen is higher than the 1st ionisation energy of Oxygen.
