Atomic, Nuclear Properties and Electromagnetic Radiation

What is the letter, number and units that denote Planck’s Constant?

h = 6.63 × 10^-34 J-s

Describe the Pauli Exclusion Principle

No 2 electrons can occupy the same state in an atom.

What is the formula and units for the radius of an atom?

r = n²a^o (nm)

Where,

• n = shell number

• a^o = 0.0529nm

What is Bohr’s Radius?

The radius of an atom when n=1, equal to a^o (0.0529nm)

What is ground state in terms of electron orbital energy levels?

The lowest energy level that occurs when n=1, therefore is -13.6eV

What is the formula and units for the energy of an electron orbit?

E = -13.6/n² (eV)

Describe Electron Binding Energy

The amount of energy that keeps an electron bound to an atom, equal to ionisation energy.

Name and describe the 2 factors that affect Electron Binding Energy

• Shell number (n) - as n decreases, electron binding energy increases

• Atomic size - as atomic size increases, electron binding energy also increases

Explain the uncertainty principle and how classical and quantum physics contribute

The uncertainty principle explains the barriers and limitations of precisely knowing measurements about particles.

• Classical physics offers no uncertainty to measurements

• However quantum physics predicts small uncertainties, eg. Simultaneous measurements of a particles location and momentum suggests that knowing location more precisely corresponds to knowing momentum less precisely and vice versa.

Give the formula and units for energy of a particle and break down the formula.

E = h x f (J)

= h x c/λ (J)

Where,

• h = Planck’s Constant (J-s)

• f = frequency (Hz)

• c = speed of light (3×10⁸)

• λ = wavelength (nm)

Give the formula for wavelength of a particle

λ = h/mv

Where,

• h = Planck’s Constant (J-s)

• m = mass of particle (kg)

• v = velocity of particle (m/s)

What is a femtometer

1 fm = 10^-15 m

Give the formula and units for the average radius of a nucleus

r = r_oA^1/3 (fm)

Where,

• r_o = 1.2 fm

• A = mass number (number of nucleons)

Explain why all nuclei have similar density

The volume and mass of nuclei are directly proportional to the number of nucleons.

Explain nuclear stability referring to the 2 nuclear forces.

The nucleus contains 2 forces, Coulomb and nuclear forces. Coulomb forces are repulsive forces between protons that should cause a nucleus to split. However, nuclear forces are stronger than Coulomb forces and are attractive forces between all nuclear particles, keeping the nucleus stable.

Explain the stability of light and heavy nuclei.

• Light nuclei are more stable when N = Z

• Heavy nuclei are more stable when N > Z as more neutrons are required to keep the nucleus stable while Z value and Coulomb forces increase

When do nuclei become unstable

When Z > 83

Explain the binding energy of nuclei.

The amount of energy required to separate nucleons.

Explain how binding energy of a nucleus and nucleon is calculated including units.

1. Calculate mass defect (combined mass of each nucleon - total mass of nucleus) in u

2. Multiply the mass defect by 931.5 MeV/u for the binding energy of the nucleus in MeV

3. Divide the binding energy by A value for the binding energy per nucleon in MeV

Give the formula and units for decay rate/activity

R = λN

Where,

• λ = decay constant

• N = number of particles

Give the formula to convert Curie to Becquerels

Ci = Bq/3.7 × 10¹⁰

Order the mass of electrons, protons and neutrons from lightest to heaviest

• Electron

• Proton

• Neutron

Explain the relationship between the movement of charges and electric and magnetic fields

• Stationary charges produce an electric field

• Charges with constant velocity produce electric and magnetic fields

• Accelerating chargers produce electric fields, magnetic fields and electromagnetic waves

Explain why electromagnetic waves are considered transverse waves.

Because the electric and magnetic fields are orientated perpendicular to one another and both are perpendicular to the direction of motion.

Why is light considered a type of electromagnetic wave

Electromagnetic waves travel at the speed of light, therefore light is an electromagnetic wave.

Give the units for the different types of electromagnetic waves.

• Larger such as radio and microwaves have units of frequency (Hz)

• Moderate such as infrared and visible light have units of m

• Smaller such as x and gamma rays have units of energy (eV)

List the 5 behaviours of electromagnetic waves.

• Reflection

• Absorption

• Diffraction

• Scatter

• Refraction

Explain reflection

Incident light hitting and bouncing off an object.

Explain absorption

Incident light hits an object, causing atoms within the object to vibrate and release heat.

Explain diffraction

Waves bending and spreading around an object, typically when the object has a similar size to the wavelength.

Explain a spectrometer.

A spectrometer utilizes diffraction to separate light into a spectrum of different wavelengths, creating a spectral signature.

Explain scatter

Scatter involves light bouncing off an object in a variety of directions.

Explain refraction

Light bending and changing direction as it passes through a different medium.

Order the speed of light as it travels through air, water and a vacuum from fastest to slowest.

• Vacuum

• Air

• Water

Order the types of electromagnetic waves from largest to smallest.

• Radiowaves

• Microwaves

• Infrared waves

• Visible light

• Ultraviolet waves

• X-rays

• Gamma rays

Explain how a radio works to produce sound.

Radio receives different wavelengths of radiowaves and convert them into vibrations, creating sound waves.

Name 3 uses of microwaves

• Heating food

• Predicting the weather forecast

• GPS tracking

Give 1 use of infrared waves and explain how they are detected

• Remote controls changing TV channels

Infrared waves are not visible by the naked eye but can be detected as heat through night-vision goggles and infrared cameras.

Explain the range of visible light.

The smallest and only segment of electromagnetic waves visible to the human eye, between 400-700nm.

Explain and describe how UV waves are divided.

• UV-A

• UV-B - harmful rays causing sunburn, however 95% absorbed by the ozone layer in the atmosphere

• UV-C - most harmful, however almost completely absorbed by the atmosphere

Explain the difference between soft and hard x-rays.

Soft x-rays have a larger wavelength and lower energy than hard x-rays

Explain the difference between ionising and non-ionising radiation.

Ionising radiation has a larger amount of energy that allows it to eject an electron from an atom, whereas non-ionising does not have enough energy to do this.

Explain the difference between electromagnetic and particulate radiation in terms of their process of ionisation.

• Electromagnetic radiation is indirectly ionising as photons collide with a target, transferring the energy that is absorbed to remove an electron.

• Whereas particulate radiation is directly ionising as the particles directly interact with the target to remove an electron.

Give the ionisation rates of EM waves, alpha particles and beta particles

• EM waves - ~100 ion pairs per cm

• Alpha particles - ~40,000 atoms per cm

• Beta particles - several hundred atoms per cm

Explain the photoelectric effect and how it demonstrates the particle nature of light.

Photoelectric effect involves electrons being emitted from a material when light hits it. This shows that light can act as photons to transfer energy and dislodge an electron within a material.