Ionisation Flashcards
First ionisation energy
The energy required to remove 1 electron from every atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions
Second ionisation energy
Energy required to remove 1 electron from every ion in one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions
Successive ionisation energies
The energy required to remove the electrons one after the other
requires more energy each time because an ion of increasingly larger pos charge is formed with greater attraction to electron
When writing ionisation equation
(g) state symbol
Only 1 electron is removed
Charge increases
The number of successive ionisation energies is the same as the charge formed on positive ion
How does the electron in ionisation energy get removed?
The energy supplied is used to overcome the electrostatic attraction between negative electron and positive nucleus and remove electron
What does the ionisation energy depend upon?
How strong the electrostatic attraction between the nucleus and electron is
Strong attraction requires more energy to overcome so higher ionisation energy
What happens if the electrostatic attraction between the ionising electron and nucleus is strong?
Then the ionisation energy will be large because more energy is required to overcome this attraction
What factors affect the electrostatic attraction thus the ionisation energy?
Shielding
Number of protons
Size of atom
SNS
(Spin sometimes of the electron)
How does shielding have an effect on ionisation energy?
With increased number of electrons there is more repulsion between outer shell electron and other electrons
So electron has weakened attraction to nucleus thus the ionisation energy is smaller
Nuclear charge
The positive charge produced by protons on the nucleus
Causes electrostatic attraction between electrons
How does nuclear charge/ atomic number have an effect on ionisation energy?
The greater number of protons means greater nuclear charge
So greater electrostatic attraction between the electron and nucleus
So ionisation energy is greater, requires more to overcome
Size of atom/ distance electron from nucleus
When there are more internal shells the electron is further away
And electrostatic attraction decreases sharper if it’s further away so reduces ionisation energy needed to remove electron
How does distance of atom/ distance electron is from nucleus affect ionisation energy?
If there are less internal shells between the electron and nucleus
Then electrostatic attraction increases sharply because the electron is closer to nucleus
So higher ionisation energy
Sudden jump in ionisation energies of an atom of 1 element
When the electron is in a shell closer to the nucleus
There is a decrease in distance of electron to nucleus
So increase in electrostatic attraction = increase ionisation energy
Ionisation energy trends across periods
ACROSS the period the ionisation energy INCREASES
The number goes up so more energy is required to remove electron
Why does ionisation energy INCREASE ACROSS the period?
Increased electrostatic attraction between nucleus and electron
Shielding had little effect, which reduces ie:
But nuclear charge increases thus the radius decreases so more electrostatic attraction which counteracts shielding
Why does the atomic radius decrease across the period?
Even though there is no increase in shells
The more protons have greater nuclear charge
So electrons are pulled closer to the nucleus decreasing distance between outer shell and nucleus
Ionisation energy trend down the group
Going down a group the ionisation energy decreases
So less energy is needed to overcome the electrostatic attraction
Why does ionisation energy DECREASE going DOWN the group?
One more quantum shell
And so the electron is at a higher level than the electron for element above
As a result IE decreases
But also experiences more shielding due to electron-electron repulsion as there are more electrons
Furthermore the electron is at a further distance
These overcome increase in nuclear charge.
Does the increase in atomic number affect the ionisation trends going down the group?
It would increase ionisation energy because of increased nuclear charge
But the increase in shielding and distance outweigh this thus the ionisation energy decreases
Be and B electron configurations
Be = 1s²2s²
B = 1s²2s²2p¹
Anomalies in the ionisation energy periodic table trends: Be to B
From Be to B the ionisation energy decreases
Because the singular 2p electron is in a higher energy sub shell than 2s
So it’s easier to remove the outer energy in 2p thus less energy required for B so lower ionisation energy
N and O electron configurations
N = 1s²2s²2p³
O = 1s²2s²2p⁴
Anomalies in ionisation energy trends in periodic table trends: N to O
There is a decrease in ionisation energy between N and O
Because in the 2p shell of N
The 3 electrons are unpaired
Whereas in 2p of O, 2 electrons are paired
The repulsion between electrons in O makes it easier to remove = decreased ionisation energy
