Scientist of
Quantum Theory
Quantum Theory
Which scientist proposed that electrons exhibit wave particle duality ?
Louis De Broglie.
He suggested that particles exhibit both wave like and particle like particles .
Who proposed the quantum model of the atom?
Erwin Schrödinger, based on earlier work by scientists such as Planck and Bohr.
What are quantum numbers and what do they describe?
Quantum numbers are values used to describe the energy, shape, orientation, and spin of an electron in an atom.
What is an atomic orbital?
A region or space around the nucleus where an electron is likely to be found .
What is an electron configuration?
An electron configuration shows how electrons are distributed among the orbitals of an atom, revealing its energy levels and orbital occupancy.
Which scientist concluded that the atom is mostly empty space with a small, positively charged nucleus, and how was this conclusion reached?
Ernest Rutherford.
He reached this conclusion through the gold foil experiment, where most alpha particles passed straight through the foil while a few were deflected, indicating a dense, positively charged nucleus surrounded by empty space.
What was the main limitation in Rutherford's atomic model?
Rutherford’s model showed that the atom is mostly empty space, with a positively charged nucleus at the center and electrons moving around it.However, the model could not explain why electrons do not lose energy and collapse into the nucleus or explain atomic emission spectra.
What does the principal quantum number (n) represent, and how does it affect electron energy?
The principal quantum number (n) represents the main energy level of an electron. As n increases, the electron’s energy and average distance from the nucleus increase.
Describe the general shapes of s and p orbitals?
s orbitals are spherical in shape, while p orbitals have a dumbbell shape or a figure 8.
How many electrons can occupy the n = 3 energy level? Show how this value is determined.
The maximum number of electrons is calculated using the formula 2n².
For n = 3:
2(3)² = 18 electrons.
How did Niels Bohr improve Rutherford’s atomic model to explain why atoms emit light at specific wavelengths?
Bohr proposed that electrons occupy fixed, quantized energy levels and emit or absorb energy only when transitioning between these levels.
How did the Bohr model explain the line spectrum?
The Bohr model proposed that electrons occupy fixed, quantized energy levels. The line emission spectrum demonstrated that electrons can only absorb or emit specific amounts of energy when transitioning between these levels.
What information does the angular momentum quantum number (ℓ) provide about an electron?
The angular momentum quantum number (ℓ) describes the shape of the orbital an electron occupies and determines whether the orbital is s, p, d, or f subshell.
How do p orbitals differ from each other within the same energy level?
p orbitals differ in their orientation in space (px, py, pz) but have the same energy within the same principal energy level.
What does Hund’s Rule state, and how does it affect electron arrangement in orbitals of equal energy?
Hund’s Rule states that electrons fill orbitals of equal energy singly before pairing up, with parallel spins, to minimize electron repulsion.
How did Erwin Schrödinger’s quantum mechanical model change the description of electron behavior compared to Bohr’s model?
Schrödinger described electrons as probability waves existing in orbitals rather than particles moving in fixed circular orbits.
How did Planck’s work support the idea that atoms absorb or emit energy in discrete quantities?
Planck showed that energy is absorbed or emitted in discrete packets called quanta, later called photons, supporting the idea that electrons gain or lose only specific amounts of energy.
What does the magnetic quantum number (mℓ) describe, and why is it important?
The magnetic quantum number (mℓ) describes the orientation of an orbital in space and distinguishes between orbitals of the same shape within the same energy level.
How many electrons can occupy a single orbital, and why?
A maximum of two electrons can occupy a single orbital because of the Pauli Exclusion Principle, which requires electrons to have opposite spins.
Explain why the electron configuration of an atom follows specific rules rather than electrons filling orbitals randomly.
Electron configurations follow specific rules to minimize energy and electron repulsion. The Aufbau Principle ensures lowest energy filling, the Pauli Exclusion Principle limits orbital capacity, and Hund’s Rule reduces repulsion in orbitals of equal energy.
Which scientist introduced a principle that limits our ability to know both the exact position and momentum of an electron?
Werner Heisenberg.
The Heisenberg Uncertainty Principle states that due to save nature of matter it is fundamentally impossible to predict both the exact position and the exact momentum of a quantum particle .
What is the quantum mechanical model of the atom, and how does it improve upon earlier atomic models?
The quantum mechanical model describes electrons as probability distributions within orbitals rather than fixed paths. It improves earlier models by accurately explaining electron behavior, atomic spectra, and the structure of multi-electron atoms.
Explain the significance of the spin quantum number (ms) and how it relates to the Pauli Exclusion Principle.
The spin quantum number (ms) describes the direction of an electron’s spin, either +½ or −½. According to the Pauli Exclusion Principle, no two electrons in an atom can have the same set of four quantum numbers, meaning an orbital can hold a maximum of two electrons with opposite spins.
Explain why atomic orbitals are described as probability regions rather than fixed electron paths.
According to quantum mechanics, the exact position of an electron cannot be known with certainty. Orbitals represent regions where electrons are most likely to be found rather than fixed paths, reflecting the wave-like behavior of electrons.
Why is the electron configuration 1s² 2s² 2p⁶ more stable than 1s² 2s² 2p⁴, even though both involve filled lower energy levels?
A completely filled subshell, such as 2p⁶, is more stable because electron repulsion is minimized and symmetry is maximized. The 2p⁴ configuration has unpaired electrons that increase repulsion and instability.