Quantum Mechanical Models

Q: What happens when atoms are excited by an electric current?

A: Atoms can emit light when excited by an electric current.

Q: How can we identify elements based on light?

A: We can identify elements based on the specific wavelength of light that is emitted.

Q: What causes light emission from atoms?

A: This is due to electromagnetic radiation.

Q: What is electromagnetic radiation?

A: Oscillating, perpendicular electric and magnetic fields moving through space as waves.

Q: What is the speed of electromagnetic waves?

A: Waves move at a speed of 3.0 × 10⁸ m/s.

Q: What is wavelength (λ)?

A: Shortest distance between equivalent points on a continuous wave.
Uses the unit 1 × 10⁻⁹ m.

Q: What is frequency (v)?

A: The number of complete wave cycles that pass a given point in a unit of time.
Uses the unit Hz.

Q: What are photons?

A: Energy moves in a packet or quantum of electromagnetic quanta.

Q: How does wavelength and frequency affect photon energy?

A:

• Longer wavelengths and low frequency have lower-energy photons.

• Short wavelengths with high frequencies have higher-energy photons.

Q: What is the relationship between frequency and wavelength?

A: The product of frequency and wavelength is a constant (c).
Formula: vλ = c
c = 3.0 × 10⁸ m/s.

Q: What formulas are used to calculate photon energy?

A:
Ephoton = Hv
E = hc/λ
H = 6.626 × 10⁻³⁴ J·s (Planck’s constant)

Q: What happens when sunlight (white light) passes through a prism?

A: It splits into different spectrums, showing colored light.

Q: What does each color of light represent?

A: Each colored light represents a single wavelength of light, and that pattern is called an emission spectrum.

Q: What did Niels Bohr want to explain?

A: The stability of a nuclear atom.

Q: What laws of physics was Bohr aware of before his research?

A:

• Electromagnetic energy travels in discrete packets or quanta.

• When matter absorbs energy, it can only absorb energy in an “all or none” manner.

• It cannot absorb only a part of a photon.

• Excited electrons emit a specific wavelength of light.

Q: What did Bohr believe about electron energy?

A: The total energy of each electron must be quantized.

Q: What does the Bohr Model describe about electrons?

A:

• Electrons exist in circular orbits; the electrostatic force keeps them in place.

• Electrons can only exist in a series of “allowed” orbits, each with a different amount of energy.

• While in an orbit, electrons cannot emit radiation.

• Electrons can jump between orbits by emitting/absorbing photons of energy equal to the difference in energy levels or by colliding with a highly energetic particle.

Q: How are orbits labeled in Bohr’s model?

A:

• Each orbit is labeled “n.”

• The orbit closest to the nucleus (ground state) is n = 1.

• As orbits increase, the n value also increases.

Q: What is the quantum mechanical model of the atom?

A: An atomic model in which electrons are treated as having wave characteristics.

Q: What does each orbit (or space) around the nucleus represent?

A: Each orbit allows for a specific characteristic of the electron.

Q: What are the four quantum numbers?

A: n, l, m₁, mₛ

Q: What is an atomic orbital?

A: A region in space around a nucleus that is related to a specific wave function.

Q: What does the quantum mechanical model allow us to predict?

A: The likelihood of locating an electron at a particular point in the atom.

Q: What does the electron density diagram show?

A: It allows us to predict where an electron would be found. The density is proportional to where we are more likely to see the electron.