Bohr’s atomic model, atomic spectra, quantum numbers

Bohr’s Atomic Model

1. Proposed by Niels Bohr in 1913 to address the limitations of Rutherford’s atomic model.
2. Electrons move in specific quantized orbits around the nucleus without radiating energy.
3. These orbits are called energy levels or shells, denoted by n (n = 1, 2, 3...).
4. The energy of an electron is constant in a specific orbit.
5. An electron can move to a higher orbit by absorbing energy or to a lower orbit by emitting energy.
6. The emitted or absorbed energy is in the form of photons, with energy given by E = hν, where h is Planck’s constant and ν is the frequency of radiation.
7. Explains the stability of the atom and the discrete lines in atomic spectra.

Atomic Spectra

1. When an electron transitions between energy levels, it emits or absorbs light of specific wavelengths.
2. The collection of these wavelengths forms the atomic spectrum of an element.
3. Atomic spectra are unique for each element, acting as their "fingerprint."
4. Two main types of spectra: Emission spectrum (light emitted by excited atoms) and absorption spectrum (light absorbed by atoms).
5. The Hydrogen spectrum is the simplest and consists of different series: Lyman, Balmer, Paschen, Brackett, and Pfund, based on the electron transitions.
6. The Balmer series, visible to the human eye, arises when electrons fall to the n = 2 energy level.
7. Atomic spectra provide insights into electron configuration and help in identifying elements in stars and distant galaxies.

Quantum Numbers

1. Quantum numbers describe the state of an electron in an atom, including its energy, position, and spin.
2. There are four quantum numbers:
3. Principal Quantum Number (n): Indicates the energy level or shell of an electron. Higher n corresponds to higher energy and larger orbit.
4. Azimuthal Quantum Number (l): Defines the shape of the orbital (s, p, d, f) and ranges from 0 to (n-1).
5. Magnetic Quantum Number (m_l): Specifies the orientation of an orbital in space and ranges from -l to +l.
6. Spin Quantum Number (m_s): Represents the spin of an electron, either +1/2 (clockwise) or -1/2 (counterclockwise).
7. Quantum numbers collectively define the unique address of an electron within an atom.

Key Applications

1. Bohr’s model explains the discrete spectra observed in experiments.
2. Quantum numbers are crucial for understanding electron configuration and chemical bonding.
3. Atomic spectra are used in spectroscopy for chemical analysis and astronomy.
4. Applications include laser technology, quantum computing, and nuclear physics.