| Electrons in atoms can only exist in discrete energy levels. | Discrete Energy Levels |
| In what form do electrons exist within atoms? | Electrons exist in discrete energy levels. |
| Excitation occurs when an electron gains energy from a collision with a free electron and moves up to a higher energy level. | Excitation |
| What is excitation in atomic terms? | Excitation is when an electron gains energy and moves up in energy level after colliding with a free electron. |
| Ionisation is when an electron gains enough energy to be removed from the atom entirely. This occurs if the energy of the free electron is greater than the ionisation energy. | Ionisation |
| What is ionisation in atomic structure? | Ionisation is when an electron gains enough energy to leave the atom if the energy of the free electron exceeds the ionisation energy. |
| The ionisation energy is the minimum energy required for an electron to be removed from the atom. | Ionisation Energy |
| What is ionisation energy? | Ionisation energy is the minimum energy needed to remove an electron from the atom. |
| When an excited electron returns to its original energy level (ground state), it releases the gained energy as a photon. | Photon Emission |
| What happens when an excited electron returns to its ground state? | The electron releases the gained energy as a photon. |
| A practical use of excitation is in fluorescent tubes to produce light. | Practical Use of Excitation |
| What is a practical application of excitation? | Excitation is used in fluorescent tubes to produce light. |
| Fluorescent tubes are filled with mercury vapour, across which a high voltage is applied, accelerating free electrons through the tube. | Fluorescent Tubes and Mercury Vapour |
| What substance is inside a fluorescent tube, and what happens when a high voltage is applied? | Mercury vapour is inside the tube, and the high voltage accelerates free electrons through it. |
| As free electrons collide with mercury atoms, they cause ionisation, releasing more free electrons in the process. | Ionisation in Fluorescent Tubes |
| How does ionisation occur in a fluorescent tube? | Free electrons collide with mercury atoms, causing ionisation and releasing more free electrons. |
| Free electrons collide with mercury atoms, causing excitation. When these atoms de-excite, they release photons, most of which are in the UV range. | Excitation and Photon Release |
| What happens to mercury atoms in a fluorescent tube during excitation and de-excitation? | They excite when colliding with free electrons and de-excite, releasing UV photons. |
| The fluorescent coating inside the tube absorbs UV photons, exciting electrons in the coating's atoms. Upon de-excitation, these electrons release visible light photons. | Fluorescent Coating |
| What role does the fluorescent coating play in a fluorescent tube? | It absorbs UV photons, and as electrons de-excite, they release visible light photons. |
| An electron volt (eV) is the energy gained by one electron when passing through a potential difference of 1 volt. | Electron Volt |
| What is an electron volt (eV) defined as? | An electron volt (eV) is the energy gained by one electron when passing through a potential difference of 1 volt. |
| Electron volts (eV) are used instead of joules (J) when describing energy differences between energy levels because the values are very small. | Why Electron Volts Are Used |
| Why are electron volts (eV) used instead of joules (J) for energy levels? | They are used because energy differences between levels are very small, making eV more practical. |
| Energy can be calculated as charge × voltage. | Energy in Terms of Charge and Voltage |
| How can energy be calculated in terms of charge and voltage? | Energy = charge × voltage. |
| To convert eV to joules, multiply the value by 1.6 × 10^-19. | Conversion From Electron Volts To Joules |
| How do you convert from electron volts (eV) to joules? | Multiply the value by 1.6 × 10^-19. |
| To convert joules to eV, divide the value by 1.6 × 10^-19. | Conversion From Joules to Electron Volts |
| How do you convert from joules to electron volts (eV)? | Divide the value by 1.6 × 10^-19. |
| A line spectrum is produced when light from a fluorescent tube passes through a diffraction grating or prism. | Line Spectrum |
| What does each line in a line spectrum represent? | Each line represents a different wavelength of light emitted by the tube. |
| A line spectrum contains only discrete wavelengths of light, meaning only certain photon energies are emitted. | Discrete Wavelengths in Line Spectrum |
| Why is a line spectrum considered evidence for discrete energy levels in atoms? | Because it shows that electrons can only transition between specific energy levels, emitting light with only certain wavelengths. |
| A line absorption spectrum occurs when white light passes through a cooled gas, producing a continuous spectrum with black lines. | Line Absorption Spectrum |
| What do the black lines in a line absorption spectrum represent? | They represent wavelengths that correspond to the energy difference between two energy levels in the gas atoms. |
| The difference between two energy levels in an atom is equal to the energy of a photon emitted or absorbed. | Photon Energy and Energy Levels |
| How is the difference between two energy levels calculated? | The difference is given by ΔE = E1 - E2, where E1 and E2 are energy levels. |
| Photon energy can be calculated with E = hf, where h is Planck's constant and f is the frequency of the photon. | Photon Energy Formula |
| How does the photon energy formula relate to the difference in energy levels? | hf = E1 - E2, showing that photon energy matches the exact energy difference between two levels. |
| Light exhibits both wave and particle properties. | Wave-Particle Duality of Light |
| What are examples of light acting as a wave? | Diffraction and interference. |
| What is an example of light acting as a particle? | The photoelectric effect. |
| Electrons also exhibit both wave and particle properties. | Wave-Particle Duality of Electrons |
| What demonstrates the wave nature of electrons? | Electron diffraction, as only waves can experience diffraction. |
| De Broglie proposed that if light exhibits particle properties, then particles should also have wave-like properties. | De Broglie's Hypothesis |
| What did De Broglie hypothesize about particles and wave-like properties? | De Broglie proposed that if light exhibits particle properties, then particles should also have wave-like properties. |
| The wavelength (λ) of an object is related to its momentum (p) by the equation:λ = h / mv, where h is the Planck constant. | De Broglie's Equation |
| How is the wavelength (λ) of an object related to its momentum (p)? | The wavelength (λ) is given by:
λ = h / mv, where h is the Planck constant. |
| As momentum increases, the wavelength decreases, causing less diffraction. Rings in the interference pattern move closer together. | Momentum and Wavelength Relationship |
| What happens to the wavelength and diffraction as momentum increases? | Wavelength decreases, diffraction decrease and rings in the interference pattern move closer together. |
| As momentum decreases, the wavelength increases, causing more diffraction. Rings in the interference pattern move further apart. | Effect of Decreased Momentum |
| What happens to the wavelength and diffraction as momentum decreases? | Wavelength increases, diffraction increases and rings in the interference pattern move further apart. |
| Scientists did not always agree that matter exhibited wave-particle duality. However, as experimental evidence (such as electron diffraction and the photoelectric effect) was gathered, the phenomenon was eventually accepted. | Term: Wave-Particle Duality of Matter |
| How did the scientific community come to accept the wave-particle duality of matter? | The wave-particle duality of matter was accepted as experimental evidence, such as electron diffraction and the photoelectric effect, was gathered and confirmed. |
| Knowledge and understanding of scientific concepts evolve over time based on the experimental evidence collected by the scientific community. | Change in Scientific Understanding |
| How does scientific understanding change over time? | Scientific understanding changes over time based on the experimental evidence gathered by the scientific community. |
