8.3 Atomic Spectroscopy and the Bohr Model

atomic spectroscopy

study of electromagnetic radiation absorbed and emitted by atoms

energy

When an atom absorbs ______ — in the form of heat, light, or electricity — it often reemits that energy as light.

light

Atoms of each element emit _____ of a characteristic color, containing several distinct wavelengths.

wavelength

The color of visible light is determined by its ___________.

emission spectrum

range of wavelengths emitted by a particular element; used to identify the element

the same

The emission spectrum of a particular element is always ________ (the same/different)—it consists of _______ (the same/different) bright lines at ________ (the same/different) characteristic wavelengths.

continuous

The white light spectrum is __________, meaning that there are no sudden interruptions in the intensity of light as a function of wavelength— the spectrum consists of light of all wavelengths.

discrete

The emission spectra of hydrogen, helium, and barium are not continuous—only certain ________ wavelengths of light are present.

continuous

According to classical physics, an atom composed of an electron orbiting a nucleus should emit a __________ white light spectrum. Even more problematic, the electron should lose energy as it emits the light and spirals into the nucleus. According to classical physics, an atom should not even be stable.

1/𝜆 = R (1/m^2 - 1/n^2)

Rydberg equation predicting the wavelengths of hydrogen emission spectrum

Bohr model

• electron travels around the nucleus in a circular orbit at specific, fixed distances from the nucleus

• the energy of each Bohr unit is quantized as well as the energy of the atom, relating to the electron’s position in the atom

• orbits are stationary states

• electrons orbiting the nucleus do not continuously emit radiation, only when an electron makes a transition is radiation emitted or absorbed

quantized

In the Bohr model of the hydrogen atom, electrons travel at orbits in specific, fixed distances from the nucleus. The energy of each Bohr unit is also fixed, or _________.

stationary states

Bohr called these orbits ___________________, which were really manifestations of the wave nature of the electron.

transition

Bohr further proposed that, in contradiction to the classical electromagnetic theory, an electron orbiting the nucleus in a stationary state emits no radiation. It is only when an electron jumps, or makes a _____________, from one stationary state to another that radiation is emitted or absorbed.

flame tests

simple tests where a sample is put into a flame, used to identify elements in ionic compounds in the absence of a precise analysis of a compound’s spectrum

color

Each _____ produced in flame tests represent an especially bright spectral emission line (or a combination of two or more such lines). Similar emissions form the basis of the color seen in fireworks.

absorption

Although the emission of light from elements is easier to detect, the __________ of light by elements is even more commonly used for purposes of identification.

absorption

An ___________ (emission/absorption) spectrum is measured by passing white light through the sample and observing what wavelengths are missing due to absorption by thee sample.

the same

Absorption lines are at ________ (the same/different) wavelengths as the emission lines because the processes that produce them are mirror images.

higher, lower

In emission, an electron makes a transition from a ______ (lower/higher)-energy level to a _____ (lower/higher)-energy one.

lower, higher

In absorption, the transition is between the same two energy levels as emission, but from the _____ (lower/higher) level to the ______ (lower/higher) one.

never

The transitions between stationary states in a hydrogen atom are quite unlike transitions in the macroscopic world. The electron is _____ (always/sometimes/never) observed between states; it is observed only in one state or another.

discrete

The emission spectrum of an atom consists of _______ lines because the stationary states exist only at specific, fixed energies.

difference

The energy of the photon emitted when an electron makes a transition from one stationary state to another is the energy __________ (sum/difference) between the two stationary states.

lower, longer

Transitions between stationary states that are closer together, therefore, produce light of _____ (lower/higher) energy, or ______ (shorter/longer) wavelength than transitions between stationary states that are far apart.