1.2.5
Ionisation Energy
Equation for Ionisation Energy
Equation for Ionisation Energy
The ionisation energy of an atom can be well defined by its ionisation equation.
,h_400,q_80,w_640.png)
,h_400,q_80,w_640.png)
The electrons
The electrons
- Ionisation is the reaction where one electron is removed from an atom.
- There will be one electron in the product of the equation.
- So we will always have an e− term on the right-hand side of the equation.
,h_400,q_80,w_640.png)
,h_400,q_80,w_640.png)
The charges
The charges
- We must understand the charges on the atom during the reaction.
- During ionisation, we remove one electron from an atom.
- As the negative electron is removed, the atom's charge will increase by 1.
- E.g. the second ionisation of Na converts Na+ → Na2+.
,h_400,q_80,w_640.png)
,h_400,q_80,w_640.png)
The state symbols
The state symbols
- Ionisation energies are always defined as being in the gas phase.
- So atomic species of any charge, on either side of the equation, will have the state symbol (g).
- We do not define the state of the electron - it has no state symbol.
,h_400,q_80,w_640.png)
,h_400,q_80,w_640.png)
Overall equation
Overall equation
- Putting all these three features together, we gain the ionisation energy equation.
- This is best shown by a few examples.
- The first ionisation energy equation of Na:
- Na(g) → e− + Na +(g)
- The second ionisation energy equation of Mg:
- Mg+(g) → e− + Mg 2+(g)
- The first ionisation energy equation of Na:
Ionisation Energies
Ionisation Energies
A specific amount of energy is needed to remove an electron from an atom or ion.
,h_400,q_80,w_640.png)
,h_400,q_80,w_640.png)
First ionisation energy
First ionisation energy
- The first ionisation energy is the energy required to remove an electron from every atom in a mole of atomic gas, to produce a mole of unipositive gaseous ions.


Second ionisation energy
Second ionisation energy
- The second ionisation energy is the energy required to remove an electron from every ion in a mole of unipositive gaseous ions, to produce a mole of dipositive gaseous ions.


Third ionisation energy
Third ionisation energy
- The third ionisation energy is the energy required to remove an electron from every ion in a mole of dipositive gaseous ions, to produce a mole of tripositive gaseous ions.


Fourth ionisation energy
Fourth ionisation energy
- Do you see the pattern?
,h_400,q_80,w_640.png)
,h_400,q_80,w_640.png)
Nth ionisation energy
Nth ionisation energy
- Overall we can form the equation shown here for the nth ionisation.
- Note the value n, for the nth ionisation, is the value of the charge on the ion in the PRODUCTS.
1Physical Chemistry
1.1Atoms, Molecules & Stoichiometry
1.2Atomic Structure
1.2.1Fundamental Particles
1.2.2Isotopes & Mass Number
1.2.3Electron Shells, Sub-Shells & Orbitals
1.2.4Electron Configuration
1.2.5Ionisation Energy
1.2.6Factors Affecting Ionisation Energies
1.2.7Trends of Ionisation
1.2.8Specific Impacts on Ionisation Energies
1.2.9Electron Affinity
1.2.10End of Topic Test - Atomic Structure
1.2.11A-A* (AO2/3) - Atomic Structure
1.3Chemical Bonding
1.3.1Ionic Bonding
1.3.2Covalent & Dative Bonding
1.3.3Shapes of Molecules
1.3.4Intermolecular Forces
1.3.5Intermolecular Forces 2
1.3.6Electronegativity
1.3.7Bond Length, Bond Energy, & Bond Polarity
1.3.8Metallic Bonding
1.3.9Physical Properties
1.3.10End of Topic Test - Bonding
1.3.11A-A* (AO2/3) - Bonding
1.4States of Matter
1.5Chemical Energetics
1.6Electrochemistry
1.7Equilibria
1.7.1Dynamic Equilibrium & Le Chatelier
1.7.2Kc
1.7.3Kp
1.7.4pH
1.7.5The Ionic Product of Water
1.7.6Weak Acids & Bases
1.7.7Introduction to Solubility Equilibria
1.7.8Solubility Equilibria Calculations
1.7.9Free Energy of Dissolution
1.7.10pH and Solubility
1.7.11Common-Ion Effect
1.7.12End of Topic Test - Kp & Electrochemistry
1.7.13A-A* (AO2/3) - Electrochemical Cells
1.8Partition Coefficient
1.9Reaction Kinetics
1.9.1Collision Theory
1.9.2Orders, Rate Constants & Equations
1.9.3Rate Graphs
1.9.4Rate Determining Step
1.9.5Maxwell-Boltzmann Distribution
1.9.6Catalysts
1.9.7Homogeneous Catalysts
1.9.8Heterogeneous Catalysts
1.9.9End of Topic Test - Kinetics
1.9.10End of Topic Test - Rate Equations
1.9.11A-A* (AO2/3) - Rate Equations
2Inorganic Chemistry
2.1The Periodic Table
2.2Group 2
2.3Group 17
2.4Transition Metals
3Organic Chemistry & Analysis
3.1Introduction to Organic Chemistry
3.2Hydrocarbons
3.2.1Fractional Distillation
3.2.2Cracking
3.2.3Combustion
3.2.4Chlorination
3.2.5End of Topic Test - Alkanes
3.2.6Introduction to Alkenes
3.2.7Reactions of Alkenes
3.2.8Polymerisation Reactions
3.2.9End of Topic Test - Alkenes
3.2.10Arenes
3.2.11Evidence for Structure of Arenes
3.2.12Reactions of Benzene
3.2.13End of Topic Test -Arenes
3.3Halogen Derivatives
3.4Hydroxy Compounds
3.5Carbonyl Compounds
3.6Carboxylic Acids & Derivatives
3.7Nitrogen Compounds
3.8Polymerisation
3.9Analytical Techniques
3.9.1Chromatography
3.9.2High-Performance Liquid Chromatography
3.9.3Gas Chromatography
3.9.4IR Spectroscopy
3.9.5Uses of IR Spectroscopy
3.9.6Mass Spectrometry
3.9.7Mass Spectrometry Analysis
3.9.8Nuclear Magnetic Resonance
3.9.9Carbon-13 NMR
3.9.10Proton NMR I
3.9.11Proton NMR II
3.9.12End of Topic Test - Analytical Techniques
3.9.13A-A* (AO2/3) - Analytical Techniques
Jump to other topics
1Physical Chemistry
1.1Atoms, Molecules & Stoichiometry
1.2Atomic Structure
1.2.1Fundamental Particles
1.2.2Isotopes & Mass Number
1.2.3Electron Shells, Sub-Shells & Orbitals
1.2.4Electron Configuration
1.2.5Ionisation Energy
1.2.6Factors Affecting Ionisation Energies
1.2.7Trends of Ionisation
1.2.8Specific Impacts on Ionisation Energies
1.2.9Electron Affinity
1.2.10End of Topic Test - Atomic Structure
1.2.11A-A* (AO2/3) - Atomic Structure
1.3Chemical Bonding
1.3.1Ionic Bonding
1.3.2Covalent & Dative Bonding
1.3.3Shapes of Molecules
1.3.4Intermolecular Forces
1.3.5Intermolecular Forces 2
1.3.6Electronegativity
1.3.7Bond Length, Bond Energy, & Bond Polarity
1.3.8Metallic Bonding
1.3.9Physical Properties
1.3.10End of Topic Test - Bonding
1.3.11A-A* (AO2/3) - Bonding
1.4States of Matter
1.5Chemical Energetics
1.6Electrochemistry
1.7Equilibria
1.7.1Dynamic Equilibrium & Le Chatelier
1.7.2Kc
1.7.3Kp
1.7.4pH
1.7.5The Ionic Product of Water
1.7.6Weak Acids & Bases
1.7.7Introduction to Solubility Equilibria
1.7.8Solubility Equilibria Calculations
1.7.9Free Energy of Dissolution
1.7.10pH and Solubility
1.7.11Common-Ion Effect
1.7.12End of Topic Test - Kp & Electrochemistry
1.7.13A-A* (AO2/3) - Electrochemical Cells
1.8Partition Coefficient
1.9Reaction Kinetics
1.9.1Collision Theory
1.9.2Orders, Rate Constants & Equations
1.9.3Rate Graphs
1.9.4Rate Determining Step
1.9.5Maxwell-Boltzmann Distribution
1.9.6Catalysts
1.9.7Homogeneous Catalysts
1.9.8Heterogeneous Catalysts
1.9.9End of Topic Test - Kinetics
1.9.10End of Topic Test - Rate Equations
1.9.11A-A* (AO2/3) - Rate Equations
2Inorganic Chemistry
2.1The Periodic Table
2.2Group 2
2.3Group 17
2.4Transition Metals
3Organic Chemistry & Analysis
3.1Introduction to Organic Chemistry
3.2Hydrocarbons
3.2.1Fractional Distillation
3.2.2Cracking
3.2.3Combustion
3.2.4Chlorination
3.2.5End of Topic Test - Alkanes
3.2.6Introduction to Alkenes
3.2.7Reactions of Alkenes
3.2.8Polymerisation Reactions
3.2.9End of Topic Test - Alkenes
3.2.10Arenes
3.2.11Evidence for Structure of Arenes
3.2.12Reactions of Benzene
3.2.13End of Topic Test -Arenes
3.3Halogen Derivatives
3.4Hydroxy Compounds
3.5Carbonyl Compounds
3.6Carboxylic Acids & Derivatives
3.7Nitrogen Compounds
3.8Polymerisation
3.9Analytical Techniques
3.9.1Chromatography
3.9.2High-Performance Liquid Chromatography
3.9.3Gas Chromatography
3.9.4IR Spectroscopy
3.9.5Uses of IR Spectroscopy
3.9.6Mass Spectrometry
3.9.7Mass Spectrometry Analysis
3.9.8Nuclear Magnetic Resonance
3.9.9Carbon-13 NMR
3.9.10Proton NMR I
3.9.11Proton NMR II
3.9.12End of Topic Test - Analytical Techniques
3.9.13A-A* (AO2/3) - Analytical Techniques
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