Atomic Spectra

If the energy of a photon does not match the energy difference between two energy levels in a hydrogen atom is the photon's energy absorbed?

No

In ultraviolet and visible spectroscopy what condition must occur for a photon to be absorbed?

Energy of the photon must match the energy difference between two energies that an electron can have.

True or False? An excited atom can return to its ground state by absorbing electromagnetic radiation.

False

True or False? The energy of an atom is increased when electromagnetic radiation is emitted from it?

False

An excited hydrogen atom emits light with a frequency of 1.14 x 1014 Hz to reach the energy level n = 4. In what principle quantum level did the electron begin?

Frequency and wavelength of electromagnetic radiation are related by: c = λν, where c is the speed of light (3.0 x 10^8 m/s). We have: (3.0 x 10^8 m/s)/(1.14 x 10^(14) Hz) = 2.63 x 10^(-6) m = λ. Now we can go and use the Rydberg formula. The R constant for hydrogen is 1.097 x 10^(7) m^(-1) [2], so we have: 1/λ = R(1/4² - 1/n²) 1/(λR) = 1/16 - 1/n² 1/(λR) - 1/16 = -1/n² n² = [1/16 - 1/(λR)]^(-1) = 35.93, or about 36. Hence, n = √36 = 6 is the starting energy level.

In the above spectroscopic experiment what is the most unique characteristic of the observed results? Hint: What does a typical spectrum look like?

Only specific wavelengths of light are absorbed or emitted. Spectrum consists of lines.

In the above experiment if only the absorbed wavelengths of light are detected what is the experiment called? What is the spectrum called?

Atomic absorption spectroscopy; Absorption line spectrum

In the above experiment if only the emitted wavelengths of light are detected what is the experiment called? What is the spectrum called?

Atomic emission spectroscopy; Emission line spectrum

For the hydrogen atom which statement is true? A. The transition from n = 5 to n = 3 involves greater energy than one from n = 4 to n = 2. B. The transition from n = 4 to n = 2 emits radiation of longer wavelength than the transition from n = 5 to n = 1. C. All transitions from states for which n > 1 to the n = 1 state involve the absorption of energy by the atom. D. A transition from n = 2 to some large value of n corresponds to the ionization energy of the H atom.

B. The transition from n = 4 to n = 2 emits radiation of longer wavelength than the transition from n = 5 to n = 1.

When the frequency of a photon matches the energy difference between two electronic energy levels it is called the __________ frequency condition as described by the equation __________ where v is the __________, ∆E is the __________, and h is __________.

Bohr, v = ∆E/h, frequency of the absorbed light, energy difference between the electronic energy levels, Plank constant

n the hydrogen atomic spectrum, what is the wavelength of light associated with the n = 2 to n = 1 electron transition?

D. 1.22 x 10-7 m

The meter was defined in 1963 as 1,650,763.73 wavelengths of radiation emitted by krypton-86 (it has since been redefined). What is the wavelength of this krypton-86 radiation? To what region of the electromagnetic spectrum does this wavelength correspond (i.e. infrared, ultraviolet, x-ray, etc.)? What energy does one photon of this radiation have?

D. 6.058 x 10-7 m (605.8 nm), Visible light, 3.281 x 10-19 J

Write the equation that allows one to calculate the electronic energy levels for the hydrogen atom. Do the calculated energies compare favorably with empirical observation (spectroscopic results)?

E = -hR/(n2), Yes

Can atomic spectroscopy be used to identify elements? If so why is it possible?

Yes, because each element has a unique spectral pattern or fingerprint.

Can molecular spectroscopy be used to identify molecules? If so why is it possible?

Yes, because most molecule have a common spectral pattern or fingerprint.

True or False? An electron in the n = 4 state in the hydrogen atom can go to the n = 2 state by emitting electromagnetic radiation at the appropriate frequency.

true

True or False? The energy of electromagnetic radiation increases as its frequency increases.

true

True or False? The frequency and wavelength of electromagnetic radiation are inversely proportional to each other.

true

In an atomic emission spectrum what does one line (one wavelength) represent?

. It represents the wavelength of light emitted by the gas sample.

When we say hydrogen atoms absorb a specific wavelength of light what do we mean? Use energy in your detailed explanation of what is being excited.

. We mean that a photon with a specific energy excites the electron in the hydrogen atom to a higher energy level. That is, the photon's energy matches the energy difference between two electronic energy levels.

If 1 million photons in the UV region are absorbed by a hydrogen gas sample how many electrons are excited to a higher energy level?

1 million

In 1.0 s, a 60 W bulb emits 11 J of energy in the form of infrared radiation (heat) of wavelength 1850 nm. What is the energy per photon of light emitted? How many photons of infrared radiation does the lamp generate in 1.0 s?

1.074 x 10^-19 J

Calculate the energy per photon of ultraviolet radiation of frequency 3.00 x 1015 Hz.

1.99 x10 ^-18

range in nm for visible light

400 nm-700nm

Calculate the wavelength of the radiation emitted by a hydrogen atom when an electron makes a transition from n = 4 to n = 2.

486 nm

Calculate the frequency of a photon emitted by a hydrogen atom when an electron makes a transition from the fourth to the second principal quantum level.

6.17 x 1014 Hz

What is the wavelength of radiation emitted by a hydrogen atom in a transition from the n = 6 to the n = 5 energy level?

7.46 x 10-6 m

In the hydrogen atomic spectrum, what is the wavelength of light associated with the n = 4 to n = 1 electron transition? What part of the electromagnetic spectrum is this wavelength?

9.73 x 10-8 m; UV region

In an atomic absorption spectrum what does one line (one wavelength) represent?

It represents the wavelength of light absorbed by the gas sample.

Choose the right description for the experimental setup in a spectroscopic experiment using a sample of hydrogen gas atoms as an example.

Light with many wavelengths is shone on the hydrogen sample. A detector measures wavelengths of light which are absorbed or emitted by the hydrogen atoms.

In atomic absorption (or emission) spectroscopy are all wavelengths of light absorbed (or emitted)?

no