Define the first electron affinity of an element.

The enthalpy change when one mole of gaseous atoms each gain one electron to form one mole of gaseous 1− ions, under standard conditions.

Define the standard enthalpy change of atomisation of an element.

The enthalpy change when one mole of gaseous atoms is formed from the element in its standard state.

What is a Born-Haber cycle used for?

To find a lattice energy indirectly, by applying Hess's law to a cycle of enthalpy changes that can each be measured directly.

List the enthalpy changes needed to construct a Born-Haber cycle for sodium chloride.

The enthalpy of formation of sodium chloride, the atomisation enthalpies of sodium and chlorine, the first ionisation energy of sodium, the first electron affinity of chlorine, and the lattice energy.

Edexcel A-Level Chemistry 9CH0

Atomic Structure and the Periodic Table

Topic overview Protons, neutrons, electrons and isotopes Relative atomic mass and the mass spectrum Ionisation energy and the evidence for sub-shells Orbitals and electron configuration Periodicity across a period and down a group

Bonding and Structure

Topic overview Ionic bonding Covalent bonding, dative bonding and the shapes of molecules Electronegativity, polarity and intermolecular forces Structure and properties

Redox I

Topic overview Oxidation numbers Oxidation, reduction, disproportionation and half-equations

Inorganic Chemistry and the Periodic Table

Topic overview Flame tests and how they work Thermal decomposition of nitrates and carbonates Carrying out flame tests and testing the gases Group 2 elements and their compounds Trends in Group 7 and predicting fluorine and astatine Halogen displacement reactions Disproportionation and the reactions of chlorine Halides with concentrated sulfuric acid, and the hydrogen halides Testing for halide ions with silver nitrate Testing for carbonate and hydrogencarbonate ions Testing for sulfate and ammonium ions

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Organic Chemistry I

Topic overview Formulae, homologous series and functional groups IUPAC nomenclature Types of organic reaction and structural isomerism Stereoisomerism and E/Z nomenclature Practical techniques in organic chemistry Alkanes, crude oil and combustion pollutants Radical substitution Alkenes, the double bond and hydrogenation Electrophilic addition, Markovnikov's rule and the test for an alkene Addition polymers and waste polymers Nucleophilic substitution of halogenoalkanes Rates of hydrolysis and the SN1 and SN2 mechanisms Classifying and oxidising alcohols Alcohols: practical techniques and the core practicals

Modern Analytical Techniques I

Topic overview Mass spectrometry Infrared spectroscopy and the characteristic absorptions Deducing functional groups from an infrared spectrum

Energetics I

Topic overview Enthalpy changes, standard definitions and calorimetry Hess's law and bond enthalpies

Kinetics I

Topic overview Collision theory and factors affecting rate Maxwell-Boltzmann distribution and temperature Catalysts, reaction profiles and measuring rate

Equilibrium I

Topic overview Dynamic equilibrium and Le Chatelier's principle The equilibrium constant Kc

Equilibrium II

Topic overview Partial pressures and Kp Calculating Kp and the effect of conditions

Acid-Base Equilibria

Topic overview Bronsted-Lowry acids and bases, and the pH scale Strong and weak acids, Ka and Kw Calculating pH, and titration curves Buffer solutions and the Henderson-Hasselbalch equation Buffers in blood, and the core practical

Energetics II

Topic overview Lattice energy Born-Haber cycles and electron affinity Entropy and the direction of change Gibbs free energy and thermodynamic feasibility

Redox II

Topic overview Standard electrode potentials and the hydrogen electrode Electrochemical cells, emf and cell diagrams Feasibility, the electrochemical series and disproportionation Storage cells, fuel cells and redox titrations

Transition Metals

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Kinetics II

Topic overview Rate equations, orders and the rate constant Determining orders from experiments Rate-determining step and mechanisms Arrhenius equation and activation energy

Organic Chemistry II

Topic overview Chirality Aldehydes, ketones and their oxidation Reduction and nucleophilic addition of HCN Testing for a carbonyl group: 2,4-DNPH and the iodoform reaction Carboxylic acids and their reactions Esters and acyl chlorides Reflux, extraction and recrystallisation Distillation, melting temperature and working safely

Organic Chemistry III

Topic overview The structure of benzene and the evidence for it Electrophilic substitution of benzene Nitration, halogenation, Friedel-Crafts and phenol Amines: structure and basicity Reactions of amines and preparing them Amides and condensation polymers Amino acids, zwitterions and proteins Empirical and molecular formulae from analytical data Grignard reagents and multi-step synthesis Purification techniques and the aspirin preparation

Modern Analytical Techniques II

Topic overview Carbon-13 and proton NMR Splitting, integration and the reference standard Chromatography High-resolution mass spectrometry

Energetics II

Born-Haber cycles and electron affinity

3 things to know
Papers 1 and 3

Overview

First and second electron affinities and atomisation enthalpy, building Born-Haber cycles for sodium chloride and magnesium chloride to find lattice energy, the perfect ionic model and what agreement with experimental values shows, and how polarisation gives covalent character.

What you need to know

Answer each one before you reveal it.

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Process

Which terms make up a Born-Haber cycle?

Key term

Why is the first electron affinity of an element exothermic?

Key term

Why is the second electron affinity of oxygen endothermic?

Questions from this subtopic

Each one with the model answer underneath.

1
Define the first electron affinity of an element.
Model answer
The enthalpy change when one mole of gaseous atoms each gain one electron to form one mole of gaseous 1− ions, under standard conditions.
2
Why is the first electron affinity of an element exothermic?
Model answer
The incoming electron is attracted by the nucleus of the neutral atom, so energy is released as it is drawn in.
3
Why is the second electron affinity of oxygen endothermic?
Model answer
The electron is being added to an ion that already carries a negative charge, so work must be done against the repulsion between them.
4
Define the standard enthalpy change of atomisation of an element.
Model answer
The enthalpy change when one mole of gaseous atoms is formed from the element in its standard state.
5
What is a Born-Haber cycle used for?
Model answer
To find a lattice energy indirectly, by applying Hess's law to a cycle of enthalpy changes that can each be measured directly.
6
List the enthalpy changes needed to construct a Born-Haber cycle for sodium chloride.
Model answer
The enthalpy of formation of sodium chloride, the atomisation enthalpies of sodium and chlorine, the first ionisation energy of sodium, the first electron affinity of chlorine, and the lattice energy.

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Atomic Structure and the Periodic Table

Bonding and Structure

Redox I

Inorganic Chemistry and the Periodic Table

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AAtomisation turns each element into gaseous atoms.

BIonisation energy removes electrons from the metal atoms.

CElectron affinity adds electrons to the non-metal atoms.

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