What goes on each axis of the binding energy per nucleon curve?

Binding energy per nucleon in MeV goes on the vertical axis and nucleon number goes on the horizontal axis. The horizontal axis runs from 1 up to about 240.

Where is the peak of the binding energy per nucleon curve, and what value does it reach?

The peak lies at a nucleon number of about 56, at iron. The binding energy per nucleon there is about 8.8 MeV.

What does the position of the peak tell you about iron nuclei?

Iron nuclei are the most tightly bound of all and so the most stable. Energy would have to be put in to turn an iron nucleus into anything else, whether by splitting it or by joining it to something.

Why does the curve rise steeply for very light nuclei?

In a very small nucleus each nucleon has only one or two neighbours pulling on it. Adding nucleons gives each one more neighbours, so the binding per nucleon climbs quickly.

Why does the curve fall away for the heaviest nuclei?

The strong interaction is short-ranged and binds a nucleon only to its close neighbours, while the electrostatic repulsion between protons acts right across the nucleus. In a large nucleus that long-range repulsion grows faster than the attraction, so each nucleon ends up less tightly held.

Eduqas A-Level Physics A420QS

Basic Physics

Topic overview SI base units and prefixes Checking equations for homogeneity Scalars and vectors Adding and resolving vectors Density Moments and the principle of moments Centre of gravity and equilibrium

Kinematics

Topic overview Displacement, velocity and acceleration Displacement-time graphs Velocity-time graphs and non-uniform acceleration The equations of uniformly accelerated motion Free fall, air resistance and terminal velocity Projectile motion

Dynamics

Topic overview Force and Newton's third law Free body diagrams and resultant force Newton's second law and F = ma Linear momentum Force as the rate of change of momentum Conservation of momentum in collisions

Energy Concepts

Topic overview Work done by a constant force Work done when the force is not along the motion Gravitational and elastic potential energy Kinetic energy and the work-energy relationship Conservation of energy Power, dissipative forces and efficiency

Circular Motion

Topic overview Period and frequency of rotation The radian as a measure of angle Angular velocity Centripetal acceleration and centripetal force Applying the circular motion equations

Vibrations

Topic overview Defining simple harmonic motion Frequency, period, amplitude and phase The displacement equation for simple harmonic motion Velocity in simple harmonic motion Displacement and velocity graphs The mass-spring oscillator The simple pendulum Energy in simple harmonic motion Free oscillation and damping Forced oscillation and resonance

Kinetic Theory

Topic overview The ideal gas equation of state Assumptions of the kinetic theory of gases The Avogadro constant, the mole and molar mass The kinetic theory pressure equation Molecular kinetic energy and temperature

Thermal Physics

Topic overview Internal energy Absolute zero and temperature Internal energy of an ideal monatomic gas Heat as energy in transit Thermal equilibrium Work done by a gas The first law of thermodynamics Specific heat capacity

Conduction of Electricity

Topic overview Electric charge and the coulomb Electric current and the ampere Conductors, insulators and charge carriers Drift of free electrons in a metal Deriving and using I = nAve

Resistance

Topic overview Potential difference and the volt Resistance, Ohm's law and the ohm I–V characteristics of a metal wire and a filament lamp Electrical power and energy transfer The microscopic origin of resistance Resistivity and the equation R = ρl/A Resistance and temperature Superconductivity and the transition temperature High temperature superconductors and their uses

D.C. Circuits

Topic overview Current at a junction and conservation of charge Potential difference round a circuit and conservation of energy Resistors in series Resistors in parallel The potential divider Sensing circuits with LDRs and thermistors emf and internal resistance

Capacitance

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Solids Under Stress

Topic overview Hooke's law and the spring constant Stress, strain and the Young modulus Work done in deforming a solid Crystalline, amorphous and polymeric solids Metals under stress: dislocations and ductile fracture Brittle solids and rubber under stress

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Using Radiation to Investigate Stars

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Orbits and the Wider Universe

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The Nature of Waves

Topic overview Progressive waves and energy transfer Transverse and longitudinal waves Polarisation Phase and antiphase Wave quantities and the wave equation Wave graphs and wavefronts

Wave Properties

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Refraction of Light

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Photons

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Lasers

Topic overview Stimulated emission and coherence Population inversion Two, three and four level systems Pumping and the structure of a laser The semiconductor laser and its uses

Nuclear Decay

Topic overview Spontaneous decay and the nature of α, β and γ radiation Nuclear transformation equations and nuclide notation Distinguishing α, β and γ by ionisation, penetration and range Background radiation and gamma intensity with distance Activity, the becquerel and the decay constant The exponential decay law and half-life

Particles and Nuclear Structure

Topic overview The Rutherford alpha particle scattering experiment Coulomb repulsion in the plum pudding and Rutherford models Quarks and leptons: the first generation Antiparticles, annihilation and their symbols Hadrons: baryons, antibaryons and mesons Quark composition of the proton, neutron and pions The four fundamental interactions Conservation laws in particle reactions

Nuclear Energy

Topic overview Mass–energy equivalence and E = Δmc² Mass defect, binding energy and the unified atomic mass unit Calculating binding energy per nucleon The binding energy per nucleon curve Fission, fusion and the nuclear power debate

Magnetic Fields

Topic overview The motor effect and Fleming's left-hand rule F = BIl sinθ and measuring magnetic flux density The force on a moving charge, F = Bqv sinθ The Hall effect and the Hall probe Magnetic fields due to a straight wire and a solenoid Forces between current-carrying conductors Charged particle beams and accelerators

Electromagnetic Induction

Topic overview Magnetic flux, flux linkage and the weber Faraday's law and Lenz's law Applying the laws: emf from rate of change of flux linkage Emf induced in a linear conductor moving through a field The rotating coil and the a.c. generator

Option A: Alternating CurrentsOption A

Topic overview Electromagnetic induction in a rotating coil Frequency, period, peak and rms values Mean power dissipated in a resistor Using an oscilloscope to measure voltage and frequency Inductors in a.c. circuits and inductive reactance Capacitors in a.c. circuits and capacitive reactance Phasors, phase angle and impedance Resonance in the series RCL circuit and the Q factor

Option B: Medical PhysicsOption B

Topic overview The nature and properties of X-rays X-ray production and controlling the beam Attenuation of X-rays and half-value thickness X-ray imaging, fluoroscopy and radiography Computed tomography scanning Ultrasound generation and acoustic impedance Ultrasound scanning and the Doppler technique Magnetic resonance and MRI Radiation effects on living matter and dosimetry Radionuclide tracers, the gamma camera and PET

Option C: The Physics of SportsOption C

Topic overview Centre of gravity, stability and toppling Moments in muscle systems and other sporting contexts Impulse and Newton's second law in sport The coefficient of restitution Moment of inertia Angular acceleration, torque and angular momentum Conservation of angular momentum and rotational energy Projectiles, Bernoulli's equation and drag

Option D: Energy and the EnvironmentOption D

Topic overview Thermal equilibrium and the Earth's energy balance Wien's law, the Stefan-Boltzmann law and solar radiation Melting ice, density and rising sea levels Photovoltaic cells and wind power Water power, pumped storage, fission and fusion Fuel cells, thermal conduction and insulation

Mathematical Requirements (Appendix C)

Topic overview Units, prefixes and standard form Significant figures and arithmetic means Uncertainty and how uncertainties combine Ratios, proportionality and order of magnitude estimates Rearranging and solving physics equations Logarithms, exponentials and decay Resolving vectors, Pythagoras and trigonometry Radians, small angles, areas and volumes Straight-line graphs, gradients and intercepts Tangents, areas under curves and logarithmic plots

How Science Works

Topic overview Hypotheses, predictions and scientific questions Evidence, experimental method and evaluating data Models and theories, and their limits Correlation and causation Peer review, the scientific community, ethics and society

Nuclear Energy

The binding energy per nucleon curve

3 things to know
Component 3

Overview

Recall questions on the shape of the curve and what goes on each axis, which nuclide sits at the peak and what that means for stability, why fusion of light nuclei and fission of heavy nuclei both release energy, and reading an energy release from two points on it.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Why does fusion of light nuclei release more energy per nucleon than fission of heavy nuclei?

Key term

Why is the binding energy per nucleon roughly constant for nuclei in the middle of the curve?

Key term

Describe the overall shape of the binding energy per nucleon curve.

Questions from this subtopic

Each one with the model answer underneath.

1
What goes on each axis of the binding energy per nucleon curve?
Model answer
Binding energy per nucleon in MeV goes on the vertical axis and nucleon number goes on the horizontal axis. The horizontal axis runs from 1 up to about 240.
2
Describe the overall shape of the binding energy per nucleon curve.
Model answer
It rises very steeply for the lightest nuclei, reaches a maximum near nucleon number 56, then falls away slowly all the way to the heaviest nuclei. The fall is far gentler than the initial rise.
3
Where is the peak of the binding energy per nucleon curve, and what value does it reach?
Model answer
The peak lies at a nucleon number of about 56, at iron. The binding energy per nucleon there is about 8.8 MeV.
4
What does the position of the peak tell you about iron nuclei?
Model answer
Iron nuclei are the most tightly bound of all and so the most stable. Energy would have to be put in to turn an iron nucleus into anything else, whether by splitting it or by joining it to something.
5
Why does the curve rise steeply for very light nuclei?
Model answer
In a very small nucleus each nucleon has only one or two neighbours pulling on it. Adding nucleons gives each one more neighbours, so the binding per nucleon climbs quickly.
6
Why does the curve fall away for the heaviest nuclei?
Model answer
The strong interaction is short-ranged and binds a nucleon only to its close neighbours, while the electrostatic repulsion between protons acts right across the nucleus. In a large nucleus that long-range repulsion grows faster than the attraction, so each nucleon ends up less tightly held.

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