Wednesday, October 21 st, 2015 Bohr Model of the Atom

 Brainstorm in your notes: What did Bohr’s model of the atom look like? To Review

 What did Bohr’s model of the atom look like? To Review: Bohr’s Model Nucleus Electron Orbit Energy Levels

 Fixed energy related to the orbit  Electrons cannot exist between orbits  The higher the energy level, the further it is away from the nucleus  An atom with maximum number of electrons in the outermost orbital energy level is stable (unreactive) Bohr Model of an Atom

 Further away from the nucleus means more energy.  There is no “in between” energy  Energy Levels First Second Third Fourth Fifth Increasing energy }

Quantum Mechanical Model Modern atomic theory describes the electronic structure of the atom as the probability of finding electrons within certain regions of space (orbitals). Niels Bohr & Albert Einstein

The Electron Cloud  The electron cloud represents positions where there is a probability of finding an electron.  The higher the electron density, the higher the probability that an electron may be found in that region.

There are two ways to state the location of an electron…  Quantum numbers – we will cover next time…  Electron configurations – the addresses of every electron in an atom (read the periodic table like a book!)

Atomic Orbitals – the address  Principal Quantum Number (n) = the energy level of the electron called “atomic orbitals”  The maximum number of electrons in an energy level = 2n 2  Each s-orbital can hold two electrons.  The p-sublevel can hold 6 electrons: how many orbitals are in the p-sublevel?  The D sub-level has 5 d-orbitals: so how many electrons can it hold?

Summary Starts at energy level

The closer an electron is to a proton, the more stable the atom!  The most stable location for an electron is as close to the nucleus as it can get… that is its ground state configuration.

 Aufbau Principle: electrons fill starting with the lowest energy level first  Pauli Exclusion Principle: Maximum 2 electrons per “orbital,” and electrons pair with opposite spin  Hunds’ Rule: electrons occupy orbitals with identical energy one at a time and in parallel, before pairing up Electron Configuration Rules

Orbital Modeling Activity