Lecture_17 - Todays Lecture Quantum Mechanics and Atomic...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Quantum Mechanics and Atomic Theory Today’s Lecture 12.10 Electron Spin and the Pauli Principle 12.11 Polyelectronic Atoms 12.12 The History of the Periodic Table (omit) 12.13 The Aufbau Principle and the Periodic Table 12.14 Further Development of the Polyelectronic Model 1 (optional) Electron Spin ± wave mechanics provides three quantum numbers to describe electron orbitals (n, l ,andm l ) ± Goudsmit and Uhlenbeck (1925) found that a fourth quantum number was necessary (in addition to n, l ,andm l ) to describe the emission spectra of atoms ± the hydrogen emission spectrum could be explained by assuming that an electron acts as if it spins, much as the Earth spins on its axis 2 ± there are two possibilities for electron spin, thus the forth quantum number, called the electron spin quantum number (m s ) can have only one of two values, +½ or -½
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 The Pauli Principle ± the significance of electron spin quantum number is its connection with a postulate of Wolfgang Pauli (called the Paul exclusion principle Pauli exclusion principle): ± in a given atom, no two electrons can have the same set of four quantum numbers (n, l ,m l ,m s ) ± since electrons in the same orbitals will have the same values of n, l ,m l they must have different values of m s 3 ± Pauli’sexclusion principle restated: ± an orbital can hold only two electrons and they must have opposite spins ± e.g. what are the quantum numbers for hydrogen’s one electron in the ground state? ± quantum mechanical model may be applied to other atoms besides just hydrogen a new interaction results Polyelectronic Atoms ± ± electron-electron repulsion ± the Schrödinger equation that results cannot be solved exactly - the so called electron correlation problem ± motion of one electron affects the motion of others must employ approximations to solve equation 4 ± ± the approximation allows the Schrödinger equation to be separated into a set of one-electron equations that can be solved by computers (our main assumption will be to treat all atoms as having orbitals similar to the hydrogen atom)
Background image of page 2
3 ± Aufbau principle:
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 7

Lecture_17 - Todays Lecture Quantum Mechanics and Atomic...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online