Ionisation Energy Flashcards
What does the process of ionisation produce?
Positively charged ions
How does ionisation energy occur?
An electron is removed from the outer shell of an atom
What is energy required for during ionisation?
Energy is required to overcome the attraction between the positively charged nucleus and the negatively charged electron. This is the ionisation energy
Define first ionisation energy
First ionisation energy is the energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions.
Write an equation for the first ionisation energy of: Na O Al Include state symbols in your answer
Na (g) —> Na+ (g) + e-
O (g) —> O+ (g) + e-
Al (g) —> Al+ (g) + e-
What are the 3 factors that affect ionisation energy?
1 - Nuclear charge
2 - Distance of the outermost electron from the nucleus
3 - Electron shielding
How does nuclear charge affect ionisation energy?
The greater the nuclear charge of the nucleus (more protons in the nucleus), more energy is required to overcome the attraction between the nucleus and the outermost electron.
How does distance from nucleus to outermost electron affect ionisation energy?
As the distance between the nucleus and the outermost electron increases, the attraction between them decreases. The wear the nuclear attraction, the less energy is needed to remove the outermost electron
How does electron shielding affect ionisation energy?
Electron shielding is the repulsion between electrons in different inner shells. This shielding effect reduces the net nuclear attraction from the positive nucleus on the outer shell electrons. The more inner shells there are, the greater the shielding effect and the weaker the nuclear attraction experienced by the outer electrons.
What is the trend in first ionisation energy as you go down a group?
First ionisation energy decreases as you go down a group because:
- more electron shells
- greater shielding effect
- atomic radius increases
- nuclear charge is increases but is outweighed by other factors
- nuclear attraction on the outer shell electrons decreases so less energy is needed to remove the outermost electron
What is the general trend in first ionisation energy across a period?
- Shows a general increase across a period because…
- Across a period the outer elecron fills the same shell so distance from nucleus to outermost electron stays the same
- The number of protons increases so nuclear charge increases
- Atomic radius decreases
- Therefore, there is a greater nuclear attraction on the outer electrons so more energy is required to remove the outermost electron
Even though the general trend across a period is first ionisation energy increases, explain the ‘BO problem’
The BO problem is where boron has a lower IE than beryllium even though it is after it in the period - this is the same for oxygen having a lower IE than nitrogen.
The reason for this is because (in B and Be) the outermost electron fills a new orbital in boron which requires less energy to be removed than the full atomic orbital of the outermost electron in beryllium
Define the term successive ionisation energy
Successive ionisation energies are a measure of the energy required to remove each electron in turn
What is the equation for the third ionisation energy of nitrogen?
N2+(g) —> N3+(g) + e-
How do you identify an element when looking at a graph of its successive ionisation energies?
Reading from right to left, the ioniation energies will decreases after each ionisation. You can see how many electrons are in each shell because the start of a new shell means that the ionisation energy of the next electron dramatically decreases rather than a small decreases in ionisation energy USE GRAPH IN BOOKLET TO HELP EXPLAIN
