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Flashcards in Ionisation Energy Deck (12):

Definition of the first ionisation energy

Energy needed for one mole of electrons to be removed from one mole of gaseous atom

E.g M(g)- M+(g)+e-
O(g)-0+(g)+e- Examples of the First ionisation energy .

Occurs in the first shell


Definition of the Second ionisation energy

Energy required to remove one electron from each ion in 1 mole of gaseous ions to form 1 mole of gaseous ions .


What are the factors affect the ionisation energy ?

Charge of nucleus
Distance from nucleus


What happens across period?

It takes more energy to remove an electrons as you go across because the number of protons increases acorss the period positive charge on nucleus increases meaning that force of attraction pulling on outer electron increases .


What happens if you go down the group?

The first ionisation energy decreases .This is because the outer electrons being removed is further from the nucleus and more inner shells to shield the outer electron .Meaning the electrostatic attraction Is weaker on the nucleus .

Group 1 :

Lithium 520 Kj mol - 1
Sodium 495 kj mo1-1
Potassium 420 Kj mol-1

Easily loose and less stable requires less energy


Why is the second ionisation greater than the first ?

Because it requires more energy in removing ions due to the stronger electrostatic attraction in the second shells as well as its difficult to pull an electron away .


Why do carbon and nitrogen show an increase ?period2

Because the electron removed from each element is in the same 2p sub shell .These electrons occupy the orbital on their own and unpaired


Oxygen - Dipped-Period 2

Electrons are removed in the 2p shell but is paired with another electron in that level However, due to the electrostatic repulsion between two electrons in the orbital mean that it easier to remove this electron .


Why does the first ionisation energy increase for Fluorine and neon ?-Period 2

Because they have a increasing positive charge .And there is a similar pattern for period 3 where the electrons are removed from the 3 s and 3 p subshell levels.


Period 4 what happens ?

Does not increase across a period only a little .Their outer electrons always comes from a 4s sub shell because this a higher emery than 4d subshell in the transition elements


Across group- What happens

Proton increase but so does the number of 3d electrons .They provide shielding and so cancel out the effect of the extra proton so ionisation energy decreases across the d block.


Sodium /Lithium

It has 8 more protons than lithium this may increase in positive charge would increase the first ionisation energy .However, the outer electron in sodium is further away form the nucleus and has more shielding .

Lithium the outer electrons is attracted to 3 positive protons and is shielded by 2 negative electrons so there is overall charge of 1 +

Sodium attracted 11 positive protons and is shielded by 10 negative electrons so has overall charge of 1 + Outer electron in sodium is further away from the nucleus and this lowers the effect of 1 + charge and first ionisation energy is lowered.