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P1 Introductory science and methods > Atoms and Light > Flashcards

Atoms and Light Flashcards

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1
Q

What are atoms made up of?

A

Protons and neutrons and electrons

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2
Q

How are electrons arranged?

A

In orbitals around nucleus

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3
Q

How are atoms classified?

A

How many particles of each type are present

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4
Q

What is atomic number?

A

The number of protons in the nucleus

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5
Q

What is mass number?

A

The total no. of nucleons

the number of protons and neutrons in nucleus measured in atomic mass unit

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6
Q

How is atomic mass unit defined?

A

1/12 the mass of carbon

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7
Q

What is 1 atomic mass unit?

A

1.6605x10-27 kg

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8
Q

What is a chemical element?

A

A species of atom with the same atomic number

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9
Q

What is the chemical properties of each element determined by?

A

Arrangment of electrons in orbitals around nucleus

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10
Q

How many electrons can each orbital hold?

A

2 electrons

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11
Q

What is energy of electrons in each orbital?

A

Fixed

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12
Q

What is quantum mechanics?

A

Probability of finding an electron at a specific position around nucleus

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13
Q

What does Heisen Berg’s uncertainity principle state?

A

We cannot simultaneouly know the position and momentum of a particle such as an electron

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14
Q

How is each orbital observed?

A

A region of space in which there is a given probability of finding the electron (e.g. a 95% chance)

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15
Q

What is seen in 2s orbital?

A

Higher chance of electrons further away from the nucleus

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16
Q

How do you fill orbitals?

A

Order of increasing energy

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17
Q

1S orbital

A

1 represents the orbital is in energy level closest to the nucleus

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18
Q

What happens when electrons get near the nucleus?

A

The lower the energy

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19
Q

What is the order of all chemical element based on?

A

Atomic number
Chemical properties
Arrangement of electrons

20
Q

What do groups of periodic table have?

A

Similar physical or chemical characteristics

21
Q

What do periods of periodic table have?

A

Trend in atomic radius, ionization energy, electron affinity, electron negativity

22
Q

How are ions formed?

A

When atoms gain or lose electrons

net positive or negative charge

23
Q

What are Group 18 and what do they have?

A

the noble gases, they have a full valence shell (outer shell) so are unreactive (He: 1s2, Ne 1s2 2s2 2p6 etc…)

24
Q

What is electromagnetic radiation?

A

Transverse wave formed from combined oscillations of electric (E) and magnetic (B) fields

25
Q

What are the properties of electromagnetic radiation?

A
  1. Don’t need a medium to travel through
  2. Move at speed of light
  3. Wave like properties e.g. interfere, reflect, refract and diffract
26
Q

What does a vertical wave represent?

A

Electric field

27
Q

What does a horizontal wave represent?

A

Magnetic field

28
Q

What are 2 examples of Wave-Particle Duality

A
  1. Black body radiation

2. Photoelectric effect and compton effect

29
Q

What is Black body radiation?

A

“black body”, an object that absorbs all electromagnetic radiation that falls upon it – none passes through and none is reflected. Since no light is reflected or transmitted, the object appears black when it is cold. However, above absolute zero, a black body emits thermal radiation with a spectrum that depends on temperature

30
Q

What is photoelectric effect?

A

When a metallic surface is exposed to electromagnetic radiation, above a certain threshold frequency, the light is absorbed and electrons are emitted (see figure, right). In 1902, Philipp Eduard Anton von Lenard observed that the energy of individual emitted electrons increases with the frequency of the light. This was at odds with Maxwell’s wave theory of light, which predicted that the electron energy would be proportional to the intensity of the radiation. In 1905, Einstein resolved this paradox by describing light as composed of discrete quanta (photons), rather than continuous waves.

31
Q

What is Compton scattering?

A

In 1923, Compton investigated the scattering of high energy X-rays and &-ray from electrons in a carbon target. By measuring the spectrum of radiation at different angles relative to the incident beam, he found two scattering peaks. The first peak occurred at a wavelength which matched that of the incident beam, while the second varied with angle. Within the framework of a purely classical theory of the scattering of electromagnetic radiation from a charged particle – Thomson scattering – the wavelength of a low-intensity beam should remain unchanged. Compton’s observation demonstrated that light cannot be explained purely as a classical wave phenomenon. Light must behave as if it consists of particles in order to explain the low-intensity Compton scattering. If one assumes that the radiation is comprised of photons that have a well defined momentum the shift in wavelength can be understood

32
Q

What are discrete particles of EM radiation called?

A

Photons

33
Q

What does EM radiation behave as?

A

Particles with discrete amount of energy and . momentum

34
Q

What are energy (E) and momentum (P) of photons related to?

A

Frequency and wavelength of EM radiation via planck’s constant

35
Q

What can we think of EM radiation as?

A

Either waves or particles

36
Q

What are typically very small?

A

Energy of atoms and sub-atomic particles

37
Q

How is energy of particles expressed as?

A

electron Volt (eV)

38
Q

What is electron Volt?

A

The amount of energy gained by an electron as it is accelerated through a potential difference of 1V

39
Q

What is energy of a photon related to?

A

Frequency

40
Q

What is frequency related to?

A

Wavelength

41
Q

What is energy related to?

A

Wavelength

42
Q

What is energy difference?

A

delta E = E2-E1 between electrons in 2 orbitals

43
Q

When do electrons lose energy?

A

If the electron drops from higher energy state in orbital 2 to lower energy state in orbital 1

Energy is emitted as a photon of EM radiation

44
Q

What is frequency of photons related to?

A

Energy difference of orbitals

45
Q

When do Photon Absorption occur?

A

If an incoming photon has an energy equal to the difference in energy between the two orbitals then it will be absorbed and the electron will be excited from orbital 1 to orbital 2

46
Q

How are characteristic X-rays emitted?

A

elements such as molybdenum when electrons move between energy levels

47
Q

Why does the characteristic x-ray emission in the spectrum occur because?

A

High energy electrons from the cathode strike the molybdenum target
They knock out electrons from the lower energy levels leaving a vacancy
Electrons in the higher energy orbitals fall down to fill the gap and emit photons of EM radiation in the x-ray range

P1 Introductory science and methods (14 decks)

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