Chapter 7 - Periodicity Flashcards
What is first ionisation energy?
The energy required to remove the first electron from each atom in a mole of gaseous atoms, producing one mole of 1+ ions. It is measured in kJ mol^-1
What are the three factors affecting ionisation energy?
Atomic radius
Electron shielding
Nuclear charge
These all link to the nuclear attraction
How does atomic radius affect nuclear attraction?
It is the distance between the nucleus and electron.
The further the nucleus is from the electron, the weaker the attraction is, therefore the ionisation energy is lower and the electron is easier to remove.
How does electronic shielding affect nuclear attraction?
It is where electrons repel each other, due to both being negatively charged. This repulsion is called the shielding effect.
As a result, if shielding is high, attraction decreases and so ionisation energy is lower.
How does nuclear charge affect nuclear attraction?
The more protons the higher the nuclear charge.
This leads to a higher nuclear attraction, as a result a higher ionisation energy is required and electrons are harder to lose.
How does ionisation energy change across a period?
It increases, as there is a stronger attraction due to more protons for the same atomic radius so the attraction is stronger.
How does ionisation energy change down a group?
It decrease, as there are more shells, so atomic radius increases, therefore attraction becomes weaker and it is easier to lose electrons.
What is periodicity?
Repeating changes in properties
e.g. down a group
Why does ionisation energy drop between group 2 and 3?
It is easier to remove the electron from group 3 due to the outer shell electron filling the first orbital of a p sub-shell, which is further from the nucleus, so there is a higher energy so more energy is required to remove the electron.
Why does ionisation energy drop between group 5 and 6?
In the first 2p orbital is 2 electrons, so the electrons repel each other. This repulsion lowers the ionisation energy and makes it easier to lose as there is less attraction to the nucleus.
What is the general trend of ionisation energy in successive energies and shells?
Ionisation energy increases as ionic radius decreases so nuclear attraction increases making it harder to lose electrons.
It also has a positive nuclear charge which gets stronger with each electron lost so ionisation energy increases making it harder to lose electrons.
However electron shielding decreases which slightly increases attraction, but not enough to outweigh the overall attraction and energy required.
What do large jumps in successive ionisation energy mean?
It is a new shell.
It increases as the shell is closer to the nucleus than in the previous shell so attraction is higher making the ionisation energy increase.
What are the 5 patterns in the periodic table?
Atomic radius
Ionisation energy
Metals to non-metals
Melting point
Electrical conductivity
How does atomic radius change across a period and why?
Across a period it decreases as there is a stronger nuclear charge due to there being more protons, this means the electrons are more attracted to the nucleus therefore the radius decreases
How does atomic radius change down the group and why?
It increases, when you go down the group there are more shells and the shielding effect repels the electrons making it increase
