Understanding Atomic Spectra

• Atomic spectra are the unique patterns of light emitted by atoms when they are excited

Production of Atomic Spectra

• Atoms are excited via heating or applying an electrical field to a gas
• Excited atoms emit light of only specific wavelengths
• The emitted light can be passed through a prism or diffraction grating to separate the wavelengths
• This produces a series of discrete lines on a dark background, known as a line spectrum
• Each element has a unique atomic spectrum
• Atomic spectra can be used to identify elements
• The wavelengths of light emitted correspond to specific energy transitions within the atom
• When an electron transitions from a higher energy level to a lower energy level, a photon is emitted
• The energy of the photon is equal to the energy difference between the two levels: (E = hf), where (E) is the energy, (h) is Planck's constant, and (f) is the frequency of the light

Types of Atomic Spectra

• Emission spectra are produced by hot, low-density gases
• Absorption spectra are produced when light passes through a cool, low-density gas
• Absorption lines appear as dark lines against a continuous spectrum
• The absorption lines occur at the same wavelengths as the emission lines for that element
• Continuous spectra are produced by hot, dense objects

Bohr Model and Atomic Spectra

• Bohr's model postulates that electrons orbit the nucleus in specific energy levels
• Electrons can only occupy these discrete energy levels
• When an electron jumps from one energy level to another, it emits or absorbs a photon
• The energy of the photon corresponds to the difference in energy between the two levels
• The Bohr model successfully predicted the hydrogen spectrum
• The wavelengths in the hydrogen spectrum follow the Rydberg formula: (\frac{1}{\lambda} = R(\frac{1}{n_1^2} - \frac{1}{n_2^2})), where (R) is the Rydberg constant, (n_1) and (n_2) are integers representing the energy levels

Energy Levels

• Energy levels are quantized, meaning electrons can only have specific energy values
• The ground state is the lowest energy level an electron can occupy
• Excited states are higher energy levels that an electron can temporarily occupy when energized
• Ionization energy is the energy required to remove an electron completely from an atom
• Energy level diagrams show the arrangement of energy levels in an atom
• Transitions between energy levels result in the emission or absorption of photons with specific energies and wavelengths

Spectral Series of Hydrogen

• The hydrogen spectrum has several series of lines, each corresponding to transitions to a specific energy level
• The Lyman series involves transitions to the n=1 level and lies in the ultraviolet region
• The Balmer series involves transitions to the n=2 level and lies in the visible region
• The Paschen series involves transitions to the n=3 level and lies in the infrared region
• The Brackett series involves transitions to the n=4 level and lies in the infrared region
• The Pfund series involves transitions to the n=5 level and lies in the infrared region

Applications of Atomic Spectra

• Identifying elements in stars and other astronomical objects
• Determining the composition of unknown samples in the lab
• Developing lasers, which rely on stimulated emission of photons
• Atomic clocks, which use the precise frequencies of atomic transitions for timekeeping
• Medical diagnostics, such as measuring the concentration of elements in blood samples.