University:
Carleton University
Course:
CHEM 1001 | General Chemistry I
Academic year:

2024
Views:

395

Pages:

2
Author:

ali

Electronic Structure multielectron atoms electronic configurations QUANTUM NO. 1 determines the energy (size or shell) of the electron only 1 electron per orbital determines the shape (or subshell) + the number of orbitals, polar axis, etc. + the angular momentum s orbitals, p orbitals, d orbitals, f orbitals... 5 d orbitals in any one set SPIN QUANTUM NUMBER (m_s) m_s = ±1/2 describes the "spin" of the electron each electron behaves like a magnet, so atoms with an odd number of e's may be detected in an inhomogeneous B field. The Stern-Gerlach experiment is a famous demonstration of spin. beam of Ag atoms passed through a collimator + then a magnet: found half went up, half went down. the quantum state of an electron is specified by the orbital quantum numbers, plus an electron spin quantum number, m_s. Rule 1: The Pauli Exclusion Principle says no 2 e's in an atom may be in the same quantum state Rule 2: The Aufbau Principle electrons in atoms generally exist in their lowest energy state electron-electron repulsion: when you have more than 1 e- in an orbital, they will repel. orbital shielding: when an orbital is occupied, it shields the interaction of the outer orbital with the nucleus. This increases the energy of the outer orbital. Orbital Shielding and its Effects Alters the E levels of the orbitals Orbital shielding is dependent on the shape/specific orbital: e's in orbitals closer to the nucleus shield e's further away The 2s orbital has a lobe closer to the nucleus than the 2p, so it is less shielded: has lower E 2s orbital has lower E than 2p: fills first Hund's rule: the lowest E e- configuration in orbitals of equal E is the one with the maximum no. of unpaired e's with parallel spin As l, the orbital extends further from the nucleus. This means that the s of an orbital ↑ with l for a given n The effect is big enough that the 4s orbital is lower than 3d Valence electrons: the no. of e's in the outermost shell, short hand using noble gases. Learning Objectives: Explain orbital shielding + its effects Write the e- configuration of atoms/ions from the s + p blocks Identify any element from the e- configurations of its atom or ion Paraphrase the Pauli exclusion + Aufbau principle Hund's rule Recognize the consequences of Hund's rule on the detailed e- configuration of an atom