1.2.1 Lesson 1 Ionisation Energy 2012

Factors affecting ionisation energy

Factors affecting ionisation energyStarter:Draw an electron shell diagram of an atom of potassium.Extension:State the order of reactivity of the alkali metals.Explain this in terms of atomic structureDefine the terms first ionisation energy and successive ionisation energy;Explain that ionisation energies are influenced by nuclear charge, electron shielding and the distance of the outermost electron from the nucleus;predict from successive ionisation energies of an element:the number of electrons in each shell of an atom,the group of the element;

By the end of the lesson you should be able to:Ionisation EnergyFirst Ionisation EnergyThe energy required to remove 1 mole of electrons from one mole of gaseous atomsX(g) X+(g) + e-

Na+Factors affecting Ionisation EnergyIonisation energy values vary from element to element.Discuss with your neighbours what factors will affect how much energy is required to remove an electron from a particular atom.For each, predict how changing that factor will affect I.E.1) Nuclear chargeAs the charge in the nucleus increases the force of attraction between the nucleus and electrons will increase.Therefore increased nuclear charge leads to increased ionisation energy.2) Number of electron shells (or distance from the nucleus)As the number of shells increases the distance from the nucleus increases. This leads to a decrease in the force of attraction between the nucleus and the outer shell electrons.Therefore increased number of shells leads to decreased ionisation energy.

3) Shielding electronsElectrons orbit the nucleusAt certain times, electrons occupying the inner shells pass between the nucleus and the outer shell electrons.This shields the force of attraction between the nucleus and the outer shell electrons.The greater the number of inner shell electrons, the larger this shielding effect.Increased shielding leads to decreased ionisation energy.NaTrends in Ionisation EnergyWhen considering trends in ionisation energy you should consider each factor in turn then conclude what the overall trend will be.The trends which you may be asked to describe and explain are:Trends in 1st IE across a periodTrends in 1st IE down a groupDescribe and explain these two trends, with reference to the three factors.Trends in First Ionisation Energy:Across a periodNuclear charge increases increased force of attraction between nucleus and electron.Number of shells remains the same no effect on force of attraction.Number of shielding electrons remains the same no effect on force of attraction.Overall: increasing force of attraction between nucleus and electrons increasing first ionisation energy values across a period.

Nuclear charge increases Increased force of attraction.Number of shells increases Decreased force of attraction.Shielding effect increases Decreased force of attraction.

Trend in First Ionisation EnergyDown a group:Overall:Although the nuclear charge increases as you go down the group, so does the number of shells and the shielding effect, meaning that the force of attraction between the nucleus and the outer shell electrons decreases and so does the first ionisation energy

Evidence for the existence of electron shellsIonisation EnergyFirst Ionisation EnergyThe energy required to remove 1 mole of electrons from one mole of gaseous atomsX(g) X+(g) + e-

Second Ionisation EnergyThe energy required to remove 1 mole of electrons from one mole of gaseous 1+ ionsX+ (g) X2+(g) + e-

12Ionisation Energynth Ionisation EnergyThe energy required to remove 1 mole of electrons from one mole of gaseous (n-1)+ ionsX(n-1)+ (g) Xn+(g) + e-

NaNumber of electrons removedLog of 1st Ionisation EnergyNumber of electrons removedLog of 1st Ionisation Energy

NaNumber of electrons removedLog of 1st Ionisation Energy






NaChart12.70757017613.65896484273.84135947053.97954837474.12710479844.2201080884.30319605744.40654018044.46089784285.14921911275.2005769268

Dataionisation energyelectrons removedlog(IE)5101345602469403495404413400541660064201007425500842890094141000105158700115Li520Be900Be800C1090N1400O1310F1680Ne2080

Trends in 1st IE52090080010901400131016802080

LiBeBCNOFNeFirst Ionisation Energy (kJ/mol)

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Chart12.70757017613.65896484273.84135947053.97954837474.12710479844.2201080884.30319605744.40654018044.46089784285.14921911275.2005769268


Trends in 1st IE52090080010901400131016802080


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Chart12.70757017613.65896484273.84135947053.97954837474.12710479844.2201080884.30319605744.40654018044.46089784285.14921911275.2005769268


Trends in 1st IE52090080010901400131016802080


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Chart12.70757017613.65896484273.84135947053.97954837474.12710479844.2201080884.30319605744.40654018044.46089784285.14921911275.2005769268


Trends in 1st IE52090080010901400131016802080


Sheet2

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Chart12.70757017613.65896484273.84135947053.97954837474.12710479844.2201080884.30319605744.40654018044.46089784285.14921911275.2005769268


Trends in 1st IE52090080010901400131016802080


Sheet2

Sheet3

Chart12.70757017613.65896484273.84135947053.97954837474.12710479844.2201080884.30319605744.40654018044.46089784285.14921911275.2005769268


Trends in 1st IE52090080010901400131016802080


Sheet2

Sheet3

Chart12.70757017613.65896484273.84135947053.97954837474.12710479844.2201080884.30319605744.40654018044.46089784285.14921911275.2005769268


Trends in 1st IE52090080010901400131016802080


Sheet2

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Chart12.70757017613.65896484273.84135947053.97954837474.12710479844.2201080884.30319605744.40654018044.46089784285.14921911275.2005769268


Trends in 1st IE52090080010901400131016802080


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1.2.1 Lesson 1 Ionisation Energy 2012