Wednesday, October 21st, 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

Incr

easi

ng e

nerg

y

}

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 = 2n2

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

s

p

d

f

# of shapes (orbitals)

Max # of electrons

1 2 1

3 6 2

5 10 3

7 14 4

Sublevel

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