Chapter 5: Electrons in the Atom 5.1 Models of the Atom 5.2 Electron Arrangement in Atoms

Bell Question How is the Bohr Model related to electrons and energy? The Bohr model represented how electrons that jump energy levels when energy is absorbed and released This is not true for all elements… We need a better model!

The Wave Mechanical Model of the Atom Picture a firefly Orbitals Nothing like orbits Probability of finding the electron within a certain space Does not describe how an electron moves or when it will be in a given space.

Section 5.1 – Atomic orbitals

Atomic Orbitals Atomic orbitals represent how the electrons are arranged on an atom.

The Hydrogen Orbitals Atomic orbitals do not have an exact edge. We arbitrarily designate the orbital as the shape that contains the electron 90% of the time. This spherical orbital represents the ground state of a hydrogen atom

In the Bohr model a higher energy level was just an orbit with a larger radius. In the wave mechanical model, the higher energy states are different kinds of orbitals with different shapes.

Orbitals and Energy Each principal energy level is divided into sublevels. Labeled with numbers and letters Indicate the shape of the orbital ex. 1s

Each sublevel has a different number of orbitals s contains 1 orbital p contains 3 orbitals d contains 5 orbitals f contains 7 orbitals

The s and p types of orbitals http://www.learner.org/interactives/periodic/elementary_interactive.html

Section 5.2 – Electron arrangement in the atoms

Electron Configurations Electron configurations are like the electron’s address Indicates which sublevels and orbitals the electrons are most likely going to occupy.

Energy and Subshells 6p 5d 4f 6s 5p 4d 5s 4p Subshells are filled from the lowest energy level to increasing energy levels. 3d 4s 3p 3s 2p 2s Energy 1s

Aufbau Principle Aufbau Principle: Electrons fill sublevels (and orbitals) so that the total energy of atom is the minimum What does this mean? Electrons must fill the lowest energy sublevels and orbitals before moving on to the next higher energy sublevels/orbital.

Hund’s Rule Hund’s Rule: Place electrons in unoccupied orbitals of the same energy level before doubling up. How does this work? If you need to add 3 electrons to a p sublevel, add 1 to each before beginning to double up.

Pauli Exclusion Principle Pauli Exclusion Principle: Two electrons that occupy the same orbital must have different spins. “Spin” describes the angular momentum of the electron “Spin” is designated with an up or down arrow. How does this work? If you need to add 4 electrons to a p subshell, you’ll need to double up. When you double up, make them opposite spins.

Orbital Diagrams Orbital diagrams use boxes for orbitals and arrows for electrons. Pay close attention to the number of orbitals for each sublevel. This will determine the number of boxes that need to be drawn

Example Nitrogen 1s2 2s2 2p3 2p 2s 1s

Practice Bromine Sodium Scandium

Electron Configurations Electron configurations describe where the electrons are located in the atom by using the number of the principal energy level and the letter of the sublevel. 1s2 Principal energy level Orbital (sublevel) Number of electrons in that sublevel

1s2 2s2 2p6 …… http://www.youtube.com/watch?v=Vb6kAxwSWgU&feature=player_embedded

Diagonal Rule Follow the arrows to know the order of each sublevel

Periodic Table

Practice Calcium Bromide ion Sodium ion

Noble Gases and Noble Gas Notation Noble Gas – Group 8 of the Periodic Table. They contain full valence shells. Noble Gas Notation – Noble gas is used to represent the core (inner) electrons Spectroscopic 1s 2s 2p 3s 3p 2 6 4s 3d 10 4p 5 Br Noble gas [Ar] 4s 2 3d 10 4p 5 The “[Ar]” represents the core electrons and only the remaining electrons are shown

Writing Noble Gas Notation Find the element on the periodic table Find the nearest noble gas that has less electrons than the element. Write the noble gas in [ ]. Write the valence electrons for the element.