exam 2 Flashcards

Question

how to calculate the energy of photons of a given frequency or wavelength

Answer 1

1. when given frequency use: e = f x h where e is the energy of the photon (J) h is planks constant (6.626 x 10^-34 Js) and f is frequency (Hz) 1. when given wavelength use: c = (wavelength (m) x (frequency) where c is speed of light (3.00 x 10^8 m/s)

Answer 2

6.626 x 10^-34 Js

Answer 3

Planck's Law shows that there are packets of energy (e) that have their own unique frequency. Therefore, where the photon strikes an electron with sufficient energy, it can eject an electron that is directly related to the frequency emitted.

Answer 4

3.00 x 10^8 m/s

Answer 5

Doubling the frequency will cause the wavelength to shorten by half.

Answer 6

Answer: 4.13 x 10^-7 m c/f = wavelength where c is 3.00 x 10^8 m/s / 7.26 x 10^14 (1/s) = 4.13 x 10^-7 m which is 413 nm

Answer 7

1 m = 10^9 nm

Answer 8

442 nm x 1 m / 10^9 nm --> 3.00 x 10^8 m/s / 442 x 10^-9 m = 6.79 x 10^14 Hz (1/s)

Answer 9

multiply by planks constant: (6.626 x 10^-34 Js)x(7.26 x 10^14 Hz (1/s)) = 4.81 x 10^-19 J

Answer 10

1. find frequency using e = f x h 2. find wavelength answer: 8.29 x 10^-10 m or 0.829 nm

Answer 11

1. find energy required to break a single cc bond: 348 x 10^3 J (348 kj)/6.022 x10^23 = 5.78 x10^-19 J 2. Use planks eqaution to find frequency! 5.78x10^-19 J / 6.626 x 10^-34 Js = 8.72 x 10^14 Hz(1/s)

Answer 12

1 kj = 1 x 10^3 J

Answer 13

claim: light is a wave evidence: When light shines through two slits a diffraction pattern is visible. reasoning: This is because the waves that are propagating from each slit meet “in phase” and “out of phase” causing an interference pattern.

Answer 14

When the waves meet “in phase”, constructive interference occurs causing the wave intensity to increase. This is seen by the bright places in the pattern. When the waves meet “out of phase” (throughs facing opposite direction) , destructive interference occurs. The waves cancel each other producing the dark places in the pattern. This is how diffraction patterns indicate that light is a wave.

Answer 15

An electron in an n=1 state absorbs a photon of light, causing the electron to transition to a higher energy level. The photon must have the exact energy as the difference between levels n=1 and n=2.

Answer 16

An electron in the n=2 state releases a photon of light as the electron transitions to a lower energy level. The photon released has the exact energy as the difference between levels n=2 and n=1.

Answer 17

highest - violet (shortest wavelength) indigo blue green yellow orange red - lowest (longest wavelength)

Answer 18

There is a bigger difference in energy between levels n=3 and n=1 so a higher energy photon is emitted during that transition. A photon of yellow light is higher in energy than a photon of red light.

Answer 19

The spacing between energy levels is different for different elements. When an electron transitions to a lower level, it emits a photon with an energy that is equal to the energy difference between the two energy levels. This energy difference is not the same for different elements, so the energy, frequency, and wavelength of the photons emitted is not the same.

Answer 20

The Bohr model only works for hydrogen and implies knowledge of both the energy and position of electrons. Since we cannot know both, we use energy diagrams. These diagrams show that an electron can absorb a photon of light and move to a higher energy level or release (emit) a photon light to move to a lower energy level. These energy levels are not circular orbits and are not a specified distance from the nucleus as Bohr proposed in his model of the atom.

Answer 21

These diagrams show that an electron can absorb a photon of light and move to a higher energy level or release (emit) a photon light to move to a lower energy level. These energy levels are not circular orbits and are not a specified distance from the nucleus as Bohr proposed in his model of the atom.

Answer 22

Atoms emit different wavelengths of light due to the unique structure and energy levels of the electrons within each atom

Answer 23

Atomic Emission Spectra and Atomic Absorption Spectra both arise from the interaction of atoms with light, but they are generated in different ways and provide different information about the atoms involved.

Answer 24

occur when atoms absorb specific wavelengths of light, which causes electrons to be excited. These spectra show dark lines where light is absorbed (mostly color, with black lines). They are often used for measuring the concentration of elements in a sample.

Answer 25

result from electrons falling from high energy levels to lower energy levels, emitting light in the process. These spectra show bright lines (mostly black with highlights of color) that can be used to identify elements and study their energy levels.

Answer 26

Hydrogen: It has well-known spectral lines, such as the red line at 656 nm in the Balmer series. Sodium: It shows a characteristic yellow doublet at 589.0 nm and 589.6 nm. Copper: It has distinct lines such as 510.6 nm and 578.2 nm in its emission spectrum.

Answer 27

Electron Diffraction (Davisson and Germer Experiment, 1927) - In this experiment, electrons were fired at a crystal of nickel, and the scattered electrons were detected. de Broglie's Hypothesis Electron Interference (Young's Double-Slit Experiment with Electrons) - . In this experiment, a beam of electrons was directed through two slits, and the pattern of electrons on a screen behind the slits was recorded. Wave-Particle Duality (de Broglie and Schrödinger)

Answer 28

Claim: Spectra are direct evidence for the existence of quantized energy levels in an atom because the discrete lines in atomic spectra correspond to specific energy transitions between quantized electron orbits within the atom. Reasoning: Discrete Lines in Spectra, Energy Level Transitions, Bohr's Model of an Atom, The Rydberg Formula When atoms absorb or emit light, they do so at specific, distinct wavelengths. In an atomic emission spectrum, we see a series of bright lines, and in an absorption spectrum, we see dark lines. These lines are not continuous but occur at specific wavelengths. The fact that the spectrum consists of only discrete lines and not a smooth continuum of colors is a key piece of evidence for quantized energy levels. These spectral lines arise when an electron in an atom moves between different energy levels. For example, when an electron absorbs energy, it moves from a lower to a higher energy level. When it falls back down, it emits energy in the form of light. The energy of the emitted or absorbed light corresponds to the difference in energy between two of these discrete energy levels. If the energy levels were not quantized, meaning they could vary continuously, the emitted or absorbed light would also be spread out across a continuous spectrum, without the sharp, distinct lines we observe. The fact that only specific wavelengths of light are emitted or absorbed supports the idea that only certain energy transitions are allowed, and that these transitions correspond to specific, quantized differences between energy levels. Niels Bohr’s model of the hydrogen atom explains this phenomenon. According to Bohr, electrons can only occupy certain quantized orbits around the nucleus, and they can only absorb or emit energy in discrete amounts when they jump from one orbit to another. This directly leads to the observation of discrete spectral lines. Bohr's model was later refined, but the basic idea that energy levels are quantized remains central to our understanding of atomic structure. The Rydberg Formula: The wavelengths of the lines in the hydrogen spectrum can be predicted using the Rydberg formula, which relates the wavelengths of the emitted light to the integer values of the energy levels involved in the transition. The fact that these wavelengths can be predicted with a mathematical formula based on discrete energy levels is further evidence that atoms have quantized energy states. Conclusion: Spectra provide direct evidence for the existence of quantized energy levels because the discrete lines in an atomic spectrum correspond to specific energy transitions between fixed energy levels in the atom. If energy levels were not quantized, we would not observe these sharp spectral lines, but rather a continuous range of wavelengths. Therefore, the structure of atomic spectra supports the idea that electrons in atoms occupy quantized energy levels.

Answer 29

In 1924, Louis de Broglie proposed that all matter (not just light) could have both particle and wave characteristics. He suggested that an electron could be treated as a wave with a wavelength (λ) given by the equation:

Answer 30

The wave-like nature of electrons was formalized by Erwin Schrödinger in 1926, who developed a mathematical model (the Schrödinger equation) to describe the behavior of quantum particles. The equation treats electrons as wavefunctions, which describe the probability distribution of where an electron might be found.

Answer 31

use de Broglie's equation, which relates the wavelength (𝜆) of a particle to its momentum. in the equation : wavelength = h/p where h is Planck's constant and p is momentum of particle. p = m x v so 𝜆 = h/mv

Answer 32

The current model of the atom, known as the quantum mechanical model (or the Schrödinger model) incorporates the wave properties of electrons to explain atomic structure and behavior. This model is based on the principles of quantum mechanics, and it accounts for the wave-particle duality of electrons, which was established by de Broglie and confirmed through experiments like electron diffraction.

Answer 33

An atomic orbital is a mathematical function that describes the wave-like behavior of an electron in an atom. It represents a region of space where the probability of finding an electron is high. Essentially, it shows where an electron is most likely to be found around the nucleus of an atom. The atomic orbital is derived from the wave function (ψ) of an electron, which is a solution to Schrödinger's equation.

Answer 34

spherical, no angular nodes (only one s orbital)

Answer 35

dumbell shaped, figure 8 shaped consists of px, py, pz

Answer 36

Dalton's model portrayed atoms as solid, indivisible spheres, but was replaced by Thomson's "plum pudding" model, which introduced the idea of electrons embedded in a positive charge, after discovering the electron. Rutherford's gold foil experiment revealed that atoms have a dense nucleus, prompting Bohr to propose quantized orbits for electrons, but Schrodinger's wave model eventually replaced Bohr's fixed orbits with probabilistic electron clouds, solving problems of electron stability and orbit quantization.

Answer 37

they have an inverse relationship! As you move down a column, ionization energy decreases and atomic radii increases due to more electron shells and more electron-electron repulsion. If you move across the rows, ionization energy increases and atomic radii decreases to a strong effective nuclear force.

Answer 38

Effective nuclear charge (𝑍eff) is the net positive charge an electron feels from the nucleus, accounting for both the actual nuclear charge and the shielding from inner electrons. It increases across a period because additional protons are added, while shielding remains relatively constant, making electrons more tightly bound. to find subtract (Pro+)-(core e-) = Zeff

Answer 39

With a larger charge, there is a stronger electrostatic attraction force between the nucleus and the electrons, causing them to be pulled tightly in.

Answer 40

With a stronger effective nuclear charge, there will need to be a stronger ionization energy to break the force.

Answer 41

Coulomb’s law explains that as the effective nuclear charge increases across a period, the attraction between the nucleus and electrons strengthens, causing atomic radii to decrease.

Answer 42

Ionization energies show that electrons are removed in specific steps, with large jumps in energy required to remove electrons from different energy levels, supporting the idea of quantized energy levels. These energy jumps reflect the distinct energy levels within the atom, where each level has a specific, measurable amount of energy associated with it.

Answer 43

Coulomb's law explains that the greater the effective nuclear charge, the stronger the attraction between the nucleus and electrons, making the atom smaller. In ions, when electrons are gained or lost, the balance between nuclear charge and electron repulsion changes, causing the ion to be either larger (when gaining electrons) or smaller (when losing electrons).

Answer 44

principal quantum number (n) angular momentum quantum number (l) magnetic quantum number (m).

Answer 45

2x 6.022 x10^23 = 1.204 x 10^24

Answer 46

YOU MUST CALCULATE THEORETICAL YEILD FIRST !!!!! (53G/2.018 = 26.3 mol H2 x 1mol H20 x 18.016 g/mol H2O = 473.8 g --> (400g/473.8 g x 100 = 84%.

Answer 47

wv = (hc)/E where h = 6.626 x 10^-34 c = 3 x10^8

Answer 48

a. The absorption lines for hydrogen would appear at exactly the same wavelengths, because the energies of the photons emitted and absorbed by hydrogen are the same.

Answer 49

c. When light shines on metal there is a threshold frequency, below which no electrons are ejected from a metal.

Answer 50

30 x 10^3 = 30,000 Hz

Answer 51

The wavelength of the electron is similar in size to the atom and affects its properties, whereas the wavelength of the macroscopic object is much smaller than the object and does not affect its properties.

Answer 52

II and IV, valence electrons have different energies and different size orbitals

Answer 53

When an electron transitions from a higher energy level to a lower energy level it emits a photon.

Answer 54

Each element has different allowed energies for its electrons (ie different energy levels). Since the differences in energy between those levels are different, the energies of the photons released will also be different. Different energy photons have different colors.

Answer 55

The lines would have the same pattern (same fingerprint) but would be slightly red-shifted because of the Doppler effect (the waves of light are stretched out as that star and Earth move away from each other).

Answer 56

The absorption spectrum looks different because it shows the colors of light that are absorbed by the element (the black likes in the absorption spectrum) rather than the colors of light being emitted by the element (the colored lines in the emission spectrum). A photon of light is absorbed by the atom, causing the electron to transition from a lower energy level to a higher energy level. This results in a line on the absorption spectrum.

Answer 57

Effective nuclear charge Shell/principal quantum number of valence shell electrons

Answer 58

white light (the rainbow), emitted from the sun

Answer 59

de Broglie: all matter has wave properties and, therefore, a wavelength λ.

Answer 60

1 J = 1 kg m2 s–2

Answer 61

positive charged cation

Answer 62

Li (Lithium) has a larger radius than Li⁺ (Lithium ion) because Li+ loses an electron. With the same amount of protons but less electrons causes the attractive force to be stronger.

exam 2 Flashcards

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