Energy Unit Electrons in Orbitals

1. Atom has small positive nucleus. Bohr’s Atomic Model 1. Atom has small positive nucleus. Good start but some basic problems: 2. Electrons orbit like planets orbit the sun. Electrons do not “orbit” in circular paths. 3. Electrons orbit in certain allowed energy levels. Could not explain why negative electrons didn’t get attracted into the nucleus 4. Electrons can jump to different orbits but only by absorbing or emitting a photon of light with the correct energy content. This model only worked for Hydrogen Copyright © by McDougal Littell. All rights reserved.

Schrodinger Wave Equation Equation for probability of a single electron being found along a single axis (x-axis). Erwin Schrodinger

Heisenberg Uncertainty Principle “One cannot simultaneously determine both the position and momentum of an electron.” You can find out where the electron is, but not where it is going. OR… You can find out where the electron is going, but not where it is! Werner Heisenberg

Wave Mechanical Model Electron states are described as orbitals. An orbital is described as the probability map of an electron’s motion.

Orbitals vs. Orbits Orbitals are nothing like orbits. An orbit is a defined path An orbital is a probability map. Copyright © by McDougal Littell. All rights reserved.

These are based on the distance from the nucleus. Electron Energy Levels (Shells) These are based on the distance from the nucleus.

Copyright © by McDougal Littell. All rights reserved.

Principle Energy Levels Discrete Energy levels that are labeled with integers. 1, 2, 3, 4, 5, 6, 7 Sublevels Each Principle Energy Level is subdivided into sublevels and labeled with a letter. The letters tell the shape of the orbital. s (holds 2 e- ) p (holds 6 e- ) d (holds 10 e- ) f (holds 14 e- ) Each orbital can hold 2 electrons.

Energy Levels, Sublevels, Electrons Sublevels in main energy level (n sublevels) Number of orbitals per sublevel Electrons per sublevel electrons per level (2n2) 1 s 2 p 3 6 8 d 5 10 18 4,5,6,7 f 7 14 32

Shapes of Sublevels S sublevels are “spherical” in shape and have only 1 orbital. The S sublevel can hold a maximum of 2 electrons. Every energy level has an s sublevel. The only difference being the diameter! Copyright © by McDougal Littell. All rights reserved.

The p sublevels are dumbbell shaped and are made of 3 orbitals or “lobes”. The p sublevel can hold a maximum of 6 electrons. p sublevels are found on energy levels 2 or greater Copyright © by McDougal Littell. All rights reserved.

d sublevels are found on energy levels 3 or greater The d sublevels are four-petaled and are made of 5 orbitals or “lobes”. The d sublevel can hold a maximum of 10 electrons. d sublevels are found on energy levels 3 or greater Copyright © by McDougal Littell. All rights reserved.

The f sublevels are made of 7 orbitals or “lobes”. The f sublevel can hold a maximum of 14 electrons. f sublevels are found on energy levels 4 or greater Copyright © by McDougal Littell. All rights reserved.

Pauli Exclusion Principle No more than two electrons may occupy the same orbital and they must have opposite spins Wolfgang Pauli

Hund’s Rule The most stable arrangement of electrons is one with the maximum number of unpaired electrons. It minimizes electron-electron repulsions and stabilizes the atom. Electrons find each other very repulsive, so they too, are in a lower energy state if each “gets their own room” or in this case orbital.

Orbital filling table

Orbital Diagram for A Fluorine Atom 1s 2s 2p 3s     

Orbital Diagram for A Nitrogen Atom 1s 2s 2p 3s     

Orbital Diagram

Element Configuration notation Orbital notation Noble gas Lithium 1s22s1 ____ ____ ____ ____ ____ 1s 2s 2p [He]2s1 Beryllium 1s22s2 [He]2s2 Boron 1s22s2p1 [He]2s2p1 Carbon 1s22s2p2 [He]2s2p2 Nitrogen 1s22s2p3 1s 2s 2p [He]2s2p3 Oxygen 1s22s2p4 [He]2s2p4 Fluorine 1s22s2p5 [He]2s2p5 Neon 1s22s2p6 [He]2s2p6