Structure Of The Atom

Aprenda jogando

Responda a estas perguntas para ganhar energia, depois pesque e explore. Sem precisar de conta.

Para educadores: slides de aula, resumos de revisão prontos para usar de Structure Of The Atom (Physics, SL) — use na sua aula ou rode o tópico como atividade interativa de turma que seus aprendizes jogam como um jogo ao vivo.

Notas de aula

Rutherford's Gold Foil Experiment

α particles (helium nuclei) were fired at a thin gold foil in an evacuated chamber.
The lead container produced a collimated beam of α particles because lead absorbs them.
The gold foil was extremely thin (~10⁻⁶ m) so α particles could pass through; gold is malleable.
The evacuated chamber prevented α particles from colliding with air molecules (they travel only ~5 cm in air).
Observations: most α particles passed straight through; some deflected by small angles (<10°); a few deflected back by angles >90°.
These results led to the nuclear model: a small, dense, positively charged nucleus surrounded by electrons, with the atom mostly empty space.

Rutherford's Alpha Scattering Experiment

Nuclear Notation

Atoms consist of protons, neutrons (in the nucleus), and electrons (orbiting the nucleus).
Proton number (Z) = number of protons; nucleon number (A) = total number of protons and neutrons.
A nucleus is represented as ^A_ZX , where X is the chemical symbol.
Protons have charge +1e and mass ~1 u; neutrons have charge 0 and mass ~1 u; electrons have charge –1e and mass ~1/2000 u.
Isotopes are nuclei with the same number of protons but different numbers of neutrons.
Ionisation is the removal of an electron from an atom; excitation is an electron moving to a higher energy level without leaving the atom.

Nuclide notation

Emission Spectra

Produced by heating a low-pressure gas, which excites electrons to higher energy levels.
When electrons de-excite, they emit photons of specific energies.
Each transition corresponds to a specific wavelength, producing a discrete line on a black background.
The emission spectrum provides evidence that electrons occupy discrete energy levels.

Absorption Spectra

Produced by passing white light through a cool, low-pressure gas.
Photons with energy exactly equal to an energy level difference are absorbed.
This results in dark lines on a continuous coloured background.
The dark lines occur at the same wavelengths as the bright lines in the emission spectrum of the same element.

Spectra and Chemical Composition

Each element produces a unique set of spectral lines, like a fingerprint.
Therefore, elements can be identified by their emission or absorption spectra.
Examples: hydrogen has a strong red line at 656 nm; sodium has a yellow line at 589 nm; mercury has lines below 450 nm (blue).
Street lights and neon signs use electrical discharge to excite atoms, which then emit characteristic colours.

Photon Energy

A photon is a massless 'packet' or 'quantum' of electromagnetic energy.
Photon energy is given by E = hf or E = rac{hc}{\lambda} .
h is Planck's constant (J s), c is the speed of light (m s⁻¹), λ is wavelength (m).
Energy is directly proportional to frequency and inversely proportional to wavelength.
The energy difference between two levels is \Delta E = hf = E₂ - E₁ .
The larger the energy difference, the shorter the wavelength of the emitted or absorbed photon.

Atomic Energy Levels and Transitions

Electrons occupy discrete energy levels; the lowest is the ground state.
Excitation: electron absorbs a photon and moves to a higher level.
De-excitation: electron emits a photon and moves to a lower level.
Ionisation: electron is removed completely; ionisation energy is the minimum energy to remove an electron from the ground state.
Energy level diagrams show horizontal lines: ground state at bottom (most negative energy), excited states above, ionisation at 0 eV (or ∞).
The number of possible transitions from n=4 to n=1 is 6, producing 6 different wavelengths.

Calculating Photon Energy and Wavelength

Use E = hf = rac{hc}{\lambda} to find photon energy or wavelength.
For a transition, \Delta E = E₂ - E₁ = rac{hc}{\lambda} .
To convert eV to J, multiply by 1.6 imes 10^-19 .
Example: a transition with \Delta E = 2.86 eV gives \lambda = 435 nm.
The number of photons per second is rac{ ext{power}}{ ext{energy of one photon}} .

Slides

Step through every slide for this topic — plus flashcards and revision notes — with a free account.

CADASTRE-SE — GRÁTIS ENTRAR

Questões de prática

Prévia grátis — 8 de 64 perguntas. Cadastre-se para ver todas.

1.Which of the following best defines a photon?
Easy
- AA massless packet or quantum of electromagnetic energy
- BA negatively charged particle orbiting the nucleus
- CA positively charged particle found in the nucleus
- DA continuous wave of electromagnetic energy
2.Excitation is
Easy
- Awhen an electron is removed from or added to an atom.
- Bwhen an electron moves down an energy level emitting a photon.
- Cwhen an electron is given enough energy to move up an energy level, but not enough to leave the atom.
- Dwhen an electron is given enough energy to move up an energy level, and sometimes leave the atom.
3.Which of the following is not a feature of an emission spectrum?
Easy
- AWhen an electron transitions from a higher energy level to a lower energy level, this results in the emission of a photon
- BAn emission spectrum contains a set of discrete wavelengths, represented by coloured lines on a black background
- CAn emission spectrum is evidence to show that electrons in atoms can only transition between discrete energy levels
- DAn emission spectrum consists of a continuous spectrum containing all the colours with dark lines at certain wavelengths
4.Which of the following was not an observation made in Rutherford's scattering experiment?
Easy
- AMost of the α-particles went straight through the foil
- BSome α-particles deflected through small angles of less than 10°
- COnly a small number of α-particles deflected straight back at angles greater than 90°
- DThe gold foil emits α particles
5.In the Geiger-Marsden-Rutherford experiment, α particles are fired at a thin gold foil. Two key observations are: I. most α particles pass through the foil undeflected; II. a few α particles are deflected by large angles. Which row correctly explains these observations?
Medium
- AI: most α-particles miss the gold atoms; II: gold atoms are mostly empty space
- BI: the atom is mostly empty space so most α-particles do not interact with the nucleus; II: the nucleus is small, dense and positively charged
- CI: the charge on the nucleus is insufficient to cause deflection; II: gold nuclei are small compared to the atom
- DI: most α-particles have enough energy to pass through the atom without interacting with it; II: the charge on the nucleus is insufficient to cause large angle deflection
6.Which of the following statements about emission and absorption spectra are correct? (select all that apply)
Medium
- AAn emission spectrum is produced when electrons transition from higher to lower energy levels.
- BAn absorption spectrum consists of bright lines on a black background.
- CEach element produces a unique pattern of spectral lines.
- DAn absorption spectrum is produced by passing white light through a cool, low-pressure gas.
- EThe dark lines in an absorption spectrum occur at different wavelengths from the bright lines in the emission spectrum of the same element.
7.In an atom, protons and neutrons are found in the nucleus while electrons orbit the nucleus.
Easy
True or false?
8.The ionisation energy of an atom is the minimum energy required to remove an electron from the ground state.
Easy
True or false?

Mais perguntas

9.The diagram below shows the energy levels of a mercury atom. Which transition produces a photon with the longest wavelength?
Medium
- An = 4 to n = 1
- Bn = 3 to n = 1
- Cn = 2 to n = 1
- Dn = 4 to n = 3
10.Which of the following correctly defines an isotope?
Medium
- AAtoms of the same element with the same number of protons but different numbers of neutrons
- BAtoms of different elements with the same number of neutrons
- CAtoms that have gained or lost electrons
- DAtoms with the same mass number but different atomic numbers
11.Place the following steps in the correct order to describe how an emission spectrum is produced.
Medium
- Energy is supplied to excite electrons to higher energy levels
- Electrons transition back to lower energy levels
- Photons of specific wavelengths are emitted
- A spectrum of discrete coloured lines on a black background is observed
12.Match each term with its correct definition.
Medium
- Ionisation
- Excitation
- De-excitation
- Photon
- Removal of an electron from an atom
- Electron moves to a higher energy level
- Electron moves to a lower energy level, emitting a photon
- A massless packet of electromagnetic energy
13.How many possible wavelengths can be produced from transitions between the n = 4 excited state and the n = 1 ground state?
Medium
- A3
- B4
- C6
- D8
14.Which of the following are purposes of specific parts of the apparatus used in Rutherford's α-particle scattering experiment? (select all that apply)
Medium
- AThe lead container collimates the α-particle beam
- BThe gold foil is thin so that α particles are not all stopped
- CThe chamber is evacuated so α particles do not collide with air molecules
- DThe detector measures the mass of the α particles
- EThe gold foil emits the α particles
15.Which of the following statements about the properties of subatomic particles are correct? (select all that apply)
Medium
- AA proton has a charge of +1e
- BA neutron has a charge of 0
- CAn electron has a mass of 9.109 × 10^-31 kg
- DA proton has a mass of 1.675 × 10^-27 kg
- EAn electron has a charge of +1e
16.Which of the following are features of an absorption spectrum? (select all that apply)
Medium
- AIt is produced by passing white light through a cool, low-pressure gas
- BIt consists of dark lines on a coloured background
- COnly photons with the exact energy required to excite electrons are absorbed
- DThe dark lines correspond to the same wavelengths as the emission lines of the same element
- EIt consists of coloured lines on a black background
17.Match each term with its correct description.
Medium
- Ionisation
- Excitation
- De-excitation
- Ground state
- An electron is removed from an atom
- An electron moves to a higher energy level
- An electron moves to a lower energy level, emitting a photon
- The lowest energy level occupied by electrons in an atom
18.Match each observation from Rutherford's α-particle scattering experiment with its correct conclusion.
Medium
- Most α particles pass straight through the foil undeflected
- Some α particles are deflected through small angles of less than 10°
- Only a small number of α particles are deflected straight back at angles greater than 90°
- The atom is mostly empty space
- There is a positive nucleus at the centre of the atom
- The nucleus is extremely small and contains most of the mass and charge of the atom
19.Place the following steps in the correct order to describe how an absorption spectrum is produced.
Medium
- White light is passed through a cool, low-pressure gas
- Photons with energies equal to the difference between two energy levels are absorbed
- Electrons are excited to higher energy levels
- The resulting spectrum shows dark lines on a continuous coloured background
20.In an atom, the nucleus is approximately 100,000 times smaller than the atom itself.
Easy
True or false?
21.Each element produces a unique pattern of spectral lines, so elements can be identified by their atomic spectrum.
Easy
True or false?
22.Which of the following correctly describes the energy of a photon?
Medium
- AIt is directly proportional to its frequency
- BIt is directly proportional to its wavelength
- CIt is inversely proportional to its frequency
- DIt is independent of its wavelength
23.Which of the following statements about the difference between photons and waves is correct?
Medium
- APhotons transfer energy continuously, while waves transfer energy in discrete packets
- BPhotons transfer energy in discrete packets, while waves transfer energy continuously
- CBoth photons and waves transfer energy in discrete packets
- DBoth photons and waves transfer energy continuously
24.In a hydrogen atom, an electron transitions from n = 4 to n = 2. Which of the following correctly describes the energy and wavelength of the emitted photon compared to a transition from n = 4 to n = 1?
Medium
- ALower energy and longer wavelength
- BHigher energy and shorter wavelength
- CLower energy and shorter wavelength
- DHigher energy and longer wavelength
25.A hydrogen atom is in the n = 3 excited state. Which transition produces a photon with the highest frequency?
Hard
- An = 3 to n = 1
- Bn = 3 to n = 2
- Cn = 2 to n = 1
- Dn = 3 to n = 4
26.The energy levels of a mercury atom are shown below. Which transition emits a photon with the lowest frequency?
Medium
- An = 4 to n = 3
- Bn = 3 to n = 2
- Cn = 2 to n = 1
- Dn = 4 to n = 1
27.The diagram shows the energy levels of a hydrogen atom. How many different photon energies can be produced from transitions between the n = 1, 2, 3, and 4 levels?
Medium
- A3
- B4
- C6
- D10
28.In a Rutherford scattering experiment, a detector measures the number of α particles scattered at different angles. Which graph best represents the variation of the number of α particles n with angle θ?
Hard
- An decreases rapidly as θ increases from 0° to 90°
- Bn increases linearly as θ increases from 0° to 90°
- Cn remains constant for all angles
- Dn increases exponentially as θ increases from 0° to 90°
29.A photon of wavelength 500 nm is incident on a metal surface. The work function of the metal is 2.0 eV. What is the maximum kinetic energy of the emitted photoelectrons? (h = 6.63 × 10⁻³⁴ J s, c = 3.00 × 10⁸ m/s, 1 eV = 1.6 × 10⁻¹⁹ J)
Hard
- A0.48 eV
- B2.48 eV
- C1.52 eV
- D3.98 eV
30.Which of the following statements about the Rutherford α-particle scattering experiment are correct? (select all that apply)
Medium
- AMost α particles pass through the gold foil undeflected.
- BSome α particles are deflected by angles greater than 90°.
- CThe gold foil is very thick to ensure many collisions.
- DThe experiment is conducted in a vacuum to prevent collisions with air molecules.
- Eα particles are negatively charged.
31.Which of the following are true about emission and absorption spectra? (select all that apply)
Hard
- AAn emission spectrum consists of bright lines on a dark background.
- BAn absorption spectrum consists of dark lines on a continuous spectrum.
- CThe wavelengths of lines in an emission spectrum are the same as the dark lines in the absorption spectrum for the same element.
- DEach element has a unique set of spectral lines.
- EAn absorption spectrum is produced when a hot gas emits light.
32.In an emission spectrum, the lines correspond to the same wavelengths as the dark lines in the absorption spectrum of the same element.
Easy
True or false?
33.The energy of a photon is directly proportional to its wavelength.
Medium
True or false?
34.Match each observation from Rutherford's α-particle scattering experiment with the correct conclusion.
Medium
- Most α particles pass straight through the foil.
- Some α particles are deflected by small angles (<10°).
- A few α particles are deflected by large angles (>90°).
- The atom is mostly empty space.
- There is a positive charge concentrated at the centre of the atom.
- The nucleus is very small and contains most of the atom's mass.
35.Which transition produces a photon with the longest wavelength?
Medium
- An=4 to n=3
- Bn=3 to n=2
- Cn=2 to n=1
- Dn=4 to n=1
36.Why is the gold foil in Rutherford's α-particle scattering experiment made extremely thin (about 10⁻⁶ m)?
Medium
- ASo that α particles are not completely absorbed before they can pass through
- BSo that the gold atoms are ionised by the α particles
- CSo that the α particles are deflected through large angles
- DSo that the gold foil emits its own α particles
37.Why was the apparatus for Rutherford's α-particle scattering experiment placed inside an evacuated chamber?
Medium
- ATo stop the gold foil from oxidising
- BBecause α particles are highly ionising and would collide with air molecules
- CTo increase the speed of the α particles
- DTo prevent the detector from overheating
38.In Rutherford's scattering experiment, the α particle source is placed inside a lead container with a narrow opening. What is the purpose of the lead container?
Medium
- ATo absorb α particles emitted in unwanted directions and produce a collimated beam
- BTo increase the energy of the α particles
- CTo detect the α particles after they pass through the foil
- DTo prevent the α particles from being deflected by the gold foil
39.In a Rutherford scattering experiment, a detector measures the number n of α particles incident per unit time at various angles θ from 0° to 90°. Which graph best represents the variation of n with θ?
Medium
- An is largest at θ = 0° and drops rapidly as θ increases
- Bn is smallest at θ = 0° and rises rapidly as θ increases
- Cn is constant for all angles θ
- Dn rises to a maximum at θ = 45° and then falls
40.A student sets up an α-particle scattering experiment but forgets to evacuate the chamber. Which of the following best describes the effect on the results?
Hard
- AFewer α particles reach the detector because they collide with air molecules, so the count rate is reduced
- BThe α particles are deflected through larger angles because air molecules are positively charged
- CThe gold foil becomes radioactive and emits its own α particles
- DThe α particles travel faster because they collide with air molecules
41.Complete the definitions of the following terms.
Medium
Ionisation is the process of removing an electron from an atom. A photon is a massless packet of electromagnetic energy. A nuclide is a specific combination of protons and neutrons in a nucleus. An isotope is an atom of the same element with the same number of protons but different numbers of ____.
42.What is the name of the particle that is a massless packet of electromagnetic energy?
Easy
43.Calculate the wavelength of a photon with an energy of 1.44 × 10⁻¹⁹ J. Give your answer in nm to 3 significant figures. Use h = 6.63 × 10⁻³⁴ J s and c = 3.00 × 10⁸ m s⁻¹.
Medium
44.In a HeNe laser, electrons collide with helium atoms. When an electron de-excites from the 2s to the 1s level in helium, a photon of wavelength 632.8 nm is emitted. Calculate the energy of this photon in eV to 3 significant figures. Use h = 6.63 × 10⁻³⁴ J s, c = 3.00 × 10⁸ m s⁻¹, and 1 eV = 1.60 × 10⁻¹⁹ J.
Hard
45.The longest wavelength produced as a result of electron transitions between two of the energy levels is 4.0 × 10⁻⁶ m. Calculate the energy difference between the two levels involved, in eV. Use h = 6.63 × 10⁻³⁴ J s, c = 3.00 × 10⁸ m s⁻¹, and 1 eV = 1.60 × 10⁻¹⁹ J.
Medium
46.Complete the following sentences about atomic energy levels.
Medium
When an electron moves to a higher energy level, the atom is said to be in an ____ state. When an electron is removed from an atom, the atom becomes ____. The ionisation energy is the minimum energy required to remove an electron from the ____ state.
47.Complete the definition of a photon.
Easy
A photon is a massless ____ or quantum of electromagnetic energy.
48.The energy levels of a hydrogen atom are -0.54 eV and -3.4 eV. Calculate the energy difference between these two levels in joules. Use 1 eV = 1.6 × 10^-19 J.
Medium
49.Light of wavelength 490 nm is incident normally on a surface. The power of the light is 3.6 mW. Calculate the number of photons incident on the surface in 30 s. Give your answer in standard form to 2 significant figures.
Hard
50.Which element produces strong spectral lines in the yellow portion of the spectrum at 589 nm?
Medium
51.Calculate the energy of a photon with a frequency of 5.0 × 10¹⁴ Hz. Give your answer in joules to 2 significant figures. Use h = 6.63 × 10⁻³⁴ J s.
Medium
52.A photon has an energy of 2.0 eV. Calculate its wavelength in nm. Use h = 6.63 × 10⁻³⁴ J s, c = 3.00 × 10⁸ m/s, and 1 eV = 1.6 × 10⁻¹⁹ J.
Hard
53.Explain how atomic spectra provide evidence for the quantisation of energy in atoms.
Medium
54.State the three observations made by Rutherford in his gold foil experiment and their significance.
Medium
55.Describe how an emission spectrum is created.
Medium
56.Explain how the observation of discrete lines in an emission spectrum provides evidence for the existence of discrete energy levels in atoms.
Hard
57.Describe how air molecules can affect the results of Rutherford's α-particle scattering experiment if the chamber is not evacuated.
Hard
58.Calculate the wavelength of a photon with an energy of 1.44 × 10⁻¹⁹ J. Give your answer in nm to 3 significant figures. Use h = 6.63 × 10⁻³⁴ J s and c = 3.00 × 10⁸ m s⁻¹.
Medium
- A1242 nm
- B1518 nm
- C1380 nm
- D1656 nm
59.In a HeNe laser, electrons collide with helium atoms. When an electron de-excites from the 2s to the 1s level in helium, a photon of wavelength 632.8 nm is emitted. Calculate the energy of this photon in eV to 3 significant figures. Use h = 6.63 × 10⁻³⁴ J s, c = 3.00 × 10⁸ m s⁻¹, and 1 eV = 1.60 × 10⁻¹⁹ J.
Hard
- A0.96 eV
- B1.96 eV
- C3.96 eV
- D2.96 eV
60.The longest wavelength produced as a result of electron transitions between two of the energy levels is 4.0 × 10⁻⁶ m. Calculate the energy difference between the two levels involved, in eV. Use h = 6.63 × 10⁻³⁴ J s, c = 3.00 × 10⁸ m s⁻¹, and 1 eV = 1.60 × 10⁻¹⁹ J.
Medium
- A-0.69 eV
- B1.31 eV
- C0.31 eV
- D2.31 eV
61.The energy levels of a hydrogen atom are -0.54 eV and -3.4 eV. Calculate the energy difference between these two levels in joules. Use 1 eV = 1.6 × 10^-19 J.
Medium
- A2 J
- B1 J
- C-1 J
- D4.576e-19 J
62.Light of wavelength 490 nm is incident normally on a surface. The power of the light is 3.6 mW. Calculate the number of photons incident on the surface in 30 s. Give your answer in standard form to 2 significant figures.
Hard
- A243000000000000000 photons
- B297000000000000000 photons
- C324000000000000000 photons
- D270000000000000000 photons
63.Calculate the energy of a photon with a frequency of 5.0 × 10¹⁴ Hz. Give your answer in joules to 2 significant figures. Use h = 6.63 × 10⁻³⁴ J s.
Medium
- A-1 J
- B2 J
- C3.3e-19 J
- D1 J
64.A photon has an energy of 2.0 eV. Calculate its wavelength in nm. Use h = 6.63 × 10⁻³⁴ J s, c = 3.00 × 10⁸ m/s, and 1 eV = 1.6 × 10⁻¹⁹ J.
Hard
- A744 nm
- B620 nm
- C558 nm
- D682 nm

Unlock all 64 questions & more

Crie uma conta grátis para ver todas as perguntas, os slides, flashcards e resumos de revisão deste tópico.

CADASTRE-SE — GRÁTIS ENTRAR

Provas anteriores

A prática com provas anteriores deste tópico chega em breve.

Em breve