Atomic Models and Spectra Quiz

Bohr's Model of the Atom

• Bohr's model depicts electrons orbiting the nucleus in specific energy levels.
• Electrons can only exist in certain allowed orbits, each with a specific energy.
• Electrons do not lose energy while in these allowed orbits.
• Energy of an electron increases with increasing distance from the nucleus.
• Electrons can jump between energy levels, absorbing or emitting energy in the process.
• This energy transfer corresponds to specific wavelengths of light (like the colours in a line spectrum).
• The line spectrum of hydrogen supports the idea of quantized energy levels.
• Bohr used the line spectrum of hydrogen to develop a quantum model of the atom.
• This model was a significant step toward understanding atomic structure.

Limitations of Rutherford's Model

• Rutherford's model suggested electrons orbiting the nucleus would lose energy and spiral into the nucleus.
• This model couldn't explain why atoms remain stable.

Bohr's Experimental Work

• Bohr experimented with applying electricity and thermal energy to hydrogen gas.
• He observed a line spectrum, a spectrum consisting of only certain colours.

Quantum Theory

• Energy released or absorbed is always in discrete (separate and distinct) quantities of energy.
• Energy released or absorbed is not a continuous stream.
• The energy emitted by a heated solid is quantized.

Photoelectric Effect

• Electrons are emitted from a metal surface when it is exposed to light.

Nature of Light

• Light is a form of energy called electromagnetic radiation.
• Electromagnetic radiation is produced by oscillating electric and magnetic disturbances, or by the movement of electrically charged particles travelling through a vacuum.

Light and Matter

• At the end of the 19th century, matter and energy were viewed as distinct and unrelated.
• Matter was considered particles with mass; light was considered waves with no mass.
• The photoelectric effect changed this view.

Quantization of Energy

• Quantized means energy is released or absorbed in discrete or certain amounts.
• Continuous means energy can take on all values.

Analogies for Quantization

• Canadian currency (e.g., $1, $5, etc.) is an example of quantized values.
• A person walking up stairs (only at specific heights) offers an analogy for quantized energy.
• A person walking up a ramp (at any height) offers an analogy for continuous energy.

Spectroscopy

• Spectroscopy is the analysis of spectra to determine the properties of their source using a spectrometer.

Emission Spectrum

• The spectrum produced when electromagnetic radiation emitted by atoms is passed through a spectrometer.
• Excited atoms return to a lower energy state from a higher energy state and emit light which create a unique spectrum of lines for each element.

Types of Emission Spectra

• Continuous spectrum: Contains all wavelengths.
• Emission line spectrum: Contains only certain wavelengths.

Dispersion of White Light

• When white light passes through a prism it separates into its constituent wavelengths creating a continuous spectrum.

Line Spectrum

• An emission spectrum that only contains certain wavelengths of light.
• The unique line spectrum for each element is used by astronomers to identify different elements in stars.
• It arises when excited electrons emit energy.

Bohr Model Success

• The Bohr model was historically important because it introduced the concept of the quantization of energy in atoms.
• It gave scientists insight that paved the way for later theoretical developments.
• Bohr calculated hydrogen's energy levels that closely matched experimental data from the hydrogen emission spectrum (obtained via spectroscopy).

Bohr Model Drawbacks

• Bohr wasn't able to theoretically explain why electrons in orbits don't lose energy.
• His model was only able to explain the line spectrum of hydrogen, but not the spectra of more complex atoms.