Fundamental Principles of Spectroscopy

Meters (m)

They are inversely proportional. Higher energy corresponds to shorter wavelength.

380 nm to 750 nm

<p>Infrared (IR) spectroscopy</p> Signup and view all the answers

<p>Electromagnetic radiation can be absorbed, emitted, or scattered by atoms and molecules, providing information about their structure and composition.</p> Signup and view all the answers

<p>Energy levels in atoms and molecules exist only at specific discrete values, not as continuous ranges.</p> Signup and view all the answers

<p>UV spectroscopy can reveal the presence of conjugated systems (alternating single and double bonds) in a molecule, which absorb UV light at specific wavelengths.</p> Signup and view all the answers

<p>Mass spectrometry fragments the molecule and measures the masses of the fragments, rather than analyzing the interaction of light with the molecule.</p> Signup and view all the answers

<p>The equation is c = fλ, where c is the speed of light, f is the frequency and λ is the wavelength.</p> Signup and view all the answers

<p>Wavelength and frequency are inversely proportional. This means that as the wavelength of electromagnetic radiation increases, its frequency decreases and vice versa.</p> Signup and view all the answers

<p>The energy of electromagnetic radiation is directly proportional to its frequency. This relationship is expressed by Planck's equation: E = hν, where E is energy, h is Planck's constant, and ν is the frequency.</p> Signup and view all the answers

<p>UV radiation has a higher energy level compared to IR radiation. This is because UV radiation has a shorter wavelength and a higher frequency than IR radiation.</p> Signup and view all the answers

<p>A quanta is a fixed, discrete energy level that electrons can occupy. These energy levels are quantized, meaning they can only exist at specific values.</p> Signup and view all the answers

<p>Electrons transition to a higher energy state by absorbing electromagnetic radiation. The energy of the absorbed radiation must exactly match the energy difference between the two states involved in the transition.</p> Signup and view all the answers

<p>When an electron returns from a higher energy state to its ground state, it releases energy in the form of electromagnetic radiation. This radiation is emitted as photons, which have an energy equal to the energy difference between the two states.</p> Signup and view all the answers

<p>NMR spectroscopy detects signals from hydrogen atoms, and the signals are influenced by the chemical environment of those hydrogen atoms. Because isomers have different arrangements of atoms in space, their hydrogen atoms experience slightly different environments. These differences in environments lead to distinct NMR signals for each isomer.</p> Signup and view all the answers

<p>The constant speed of electromagnetic radiation, often called the speed of light, is significant because it allows us to relate wavelength and frequency using a simple equation. This relationship leads to predictable energy differences between different regions of the electromagnetic spectrum.</p> Signup and view all the answers

<p>The energy of the absorbed electromagnetic radiation must exactly match the energy difference between the lower energy state (E1) and the higher energy state (E2). If the energy of the radiation does not match this difference, there will be no absorption and the electron will not transition.</p> Signup and view all the answers

<p>Energy is directly proportional to frequency and inversely proportional to wavelength. This relationship is described by the equation E = hν = hc/λ, where E is energy, h is Planck's constant, ν is frequency, c is the speed of light, and λ is wavelength.</p> Signup and view all the answers

<p>Quantized energy levels mean that atoms can only exist in specific, discrete energy states. Electrons in an atom can only occupy these specific energy levels, and transitions between them occur by absorbing or emitting photons of specific energies.</p> Signup and view all the answers

<p>$E = hν = (6.63 × 10^{-34} J⋅s)(5.0 × 10^{14} Hz) = 3.315 × 10^{-19} J$</p> Signup and view all the answers

<p>Electronic energy levels relate to the energy of electrons within the molecule, vibrational energy levels correspond to the stretching and bending of chemical bonds, and rotational energy levels involve the rotation of the molecule as a whole.</p> Signup and view all the answers

<p>This wavelength corresponds to visible light (specifically, orange-red light). The absorption of visible light typically causes electronic transitions within the molecule, promoting electrons to higher energy levels.</p> Signup and view all the answers

<p>The equation <code>∆E = hv</code> states that the energy difference (<code>∆E</code>) between two energy levels in a molecule is directly proportional to the frequency (<code>v</code>) of the electromagnetic radiation absorbed. This means a molecule will only absorb radiation with a specific frequency that matches the energy difference between its energy levels.</p> Signup and view all the answers

<p>The three main types of energy levels are electronic, vibrational, and rotational. Electronic levels are related to the arrangement of electrons in molecular orbitals. Vibrational levels are related to the stretching and bending of bonds within the molecule. Rotational levels are related to the rotation of the molecule as a whole.</p> Signup and view all the answers

<p>Electronic transitions typically involve ultraviolet (UV) or visible (Vis) light. An electron in the molecule absorbs the energy from the UV/Vis light and is excited from a lower-energy electronic level (ground state) to a higher-energy electronic level (excited state).</p> Signup and view all the answers

<p>IR radiation causes vibrational energy transitions in molecules. This means the energy absorbed by the molecule causes its bonds to stretch or bend. It can also induce rotational transitions within the vibrational energy levels.</p> Signup and view all the answers

<p>Rotational-vibrational coupling refers to the simultaneous occurrence of rotational and vibrational transitions within a molecule when it absorbs IR radiation. This happens because the energy levels involved in vibrational transitions have further sub-levels associated with rotation.</p> Signup and view all the answers

<p>Visible hydrogen emission spectrum lines, including H-alpha, are caused by the emission of visible light photons when electrons in hydrogen atoms transition from higher energy levels to lower energy levels.</p> Signup and view all the answers

<p>A molecule can only absorb a particular frequency of electromagnetic radiation if there exists an energy transition within the molecule where <code>(E2 - E1) = ∆E = hv</code>. The energy levels of a molecule are quantized; they exist at specific, discrete energy values.</p> Signup and view all the answers

<p>The frequency and energy of electromagnetic radiation are directly proportional. Higher frequency radiation carries more energy, while lower frequency radiation carries less energy.</p> Signup and view all the answers

<p>Quantized energy levels mean that atoms and molecules can only exist at specific, discrete energy values. They cannot have any arbitrary energy value between these specific levels. This is unlike systems in classical physics where continuous energy values are possible.</p> Signup and view all the answers

<p>The existence of quantized energy levels explains the discrete lines observed in atomic and molecular spectra. Electrons can only transition between specific energy levels, leading to the absorption or emission of photons with specific frequencies that correspond to the energy differences between these levels.</p> Signup and view all the answers

Energy of a photon is inversely related to its wavelength.

The energy associated with a photon is given by E=hv, where h is Planck's constant and v is frequency.

To get energy per mole, multiply photon energy by Avogadro's number (6.02 x 10^23).

Electromagnetic radiation is defined by its frequency and wavelength, ranging from radio waves to gamma rays.

Energy levels in atoms are quantized, meaning they can only adopt specific energy values.

Waves with electric and magnetic fields transmitting energy through space.

The distance between consecutive peaks of an electromagnetic wave, measured in meters.

The number of wave peaks passing a point in one second, measured in hertz (Hz).

The measurement of electromagnetic radiation absorbed, scattered, or emitted by substances.

The concept that atoms and molecules have discrete energy levels.

Uses electron transitions to analyze bonding patterns in molecules.

Measures bond vibration frequencies to identify functional groups in molecules.

Ranges for different types of electromagnetic radiation: X-rays (0.01 to 10 nm), UV/VIS (10 to 750 nm), IR (750 nm to 1 mm), RF (1 mm to 1 m).

Change in energy levels when a molecule absorbs radiation.

Energy difference equation, where h is Planck's constant and v is frequency.

Main energy levels in a molecule associated with electron arrangements.

Sublevels in electronic energy levels causing molecular vibrations.

Subdivisions within vibrational levels related to molecular rotation.

Transitions when molecules absorb UV or visible light.

Changes in energy due to molecular vibrations from infrared radiation.

Phenomenon occurring when both vibrational and rotational transitions happen.

A spectroscopy technique that detects signals from hydrogen atoms to distinguish isomers.

c = fλ relates speed, frequency, and wavelength of radiation.

A fundamental constant (h = 6.63×10−34 J·s) used in quantum mechanics.

Fixed energy levels that electrons can occupy in an atom, transitioning between states.

A particle of light released when electrons drop to a lower energy state.

Wavelength is inversely proportional to frequency.

Electrons absorb energy to move from a lower to a higher energy level.

Range of all types of electromagnetic radiation based on wavelength and frequency.

Electrons move to higher energy states upon absorbing electromagnetic radiation.

When electrons lose energy and emit radiation as they drop back to a lower energy level.