15 - Periodicity Flashcards
Define ionisation energy
The energy required to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions
What is the first ionisation energy?
The energy to take off the first electron (making a 1+ iron from an atom)
What are the 3 factors which affect ionisation energy?
Charge of nucleus
Distance from nucleus
Electron shielding
What is electron shielding?
The repulsion between electrons in inner shells
What is the overall factor which affects ionisation energy?
Attraction
Attraction is affected by ionisation energy, charge of nucleus and electron shielding.
What is the relationship between overall attraction and ionisation energy?
As attraction increases
Ionisation energy also increases
What is the relationship between charge of nucleus and attraction?
As the charge of the nucleus increases, attraction increases
What is the relationship between attraction and electron shielding?
As the electron shielding increases, attraction increases
What happens to the 3 factors which affect ionisation energy as you go down a group?
Distance from nucleus increases
Charge of nucleus increases
Shielding increases
They all increase
What happens to ionisation energy (and attraction) as you go down a group?
As you go down a group, ionisation energy decreases
What happens to ionisation energy (and attraction) as you go across the groups from left to right?
Ionisation energy increases
What are the 2 exceptions to the fact that ionisation energy increases as you go across a period?
Ionisation energy decreases across a period when:
A new orbital is added (from 1s^2 2s^2 to 1s^2 2s^2 2p^1 for example)
Which happens from group 2 to 3
Or the outermost electron of an element is spin paired when the element to the left doesn’t have the outermost electron in a spin pair (outer electron in O is spin paired by not N do O has a lower IE than N despite O being to right of N)
Which happens from group 5 to 6
Why does having a spin paired outer electron decrease ionisation energy?
This electron is repelled by the other electron in the spin pair so it is much easier to remove
What are successive ionisation energies?
Measure of energy required to remove each electron in turn from each atom of 1 mole of substance
Like second, third ionisation energy
What is the chemical equation showing lithium being ionised?
Li(g) –> Li(g)+ + e-
The gas state symbols are very important
What happens to the value of ionisation energy when you go from first, to second ionisation energy and so on?
As order of ionisation energy increases, ionisation energy increases too
First IE < Second IE < Third IE and so on
What happens to ionisation energy when an outer shell is lost due to electrons being lost by ionisation?
The ionisation energy suddenly increases when an outer shell is lost
What happens to electron shielding as you go across a period and why?
It doesn’t change
Because you are filling up the same shell
Describe precisely what happens to boiling point as you go across the groups
From group 1 to 14, there is a general increase in boiling point
From group 14 to 15, there is a sharp increase in boiling point
From group 15 to 18, the boiling point is very low
Explain why silicon has a much higher boiling point than phosphorus
Silicon has strong covalent bonds but phosphorus only has London forces
Explain why boiling point increases from sodium to aluminium
Aluminium has ions with greater charge so the metallic bonds are stronger in aluminium
What is electron shielding proportional to?
The number of shells
