Transcript Atomic_Orbitals

The Atom
Objectives
Previous Unit
To know the three elementary particles which
compose atoms.
To understand the development of the atomic
model.
Let’s take this one step further…
Objectives
Unit 4
 Objective 1 - To understand the Quantum Mechanical Model
of the atom as it applies to principle energy levels and
sublevels.
 Objective 2 – Be able to apply the Aufbau Principle, the Pauli
Exclusion Principle, and Hund’s Rule in writing electron
configurations of elements, and understand why there are some
exceptions.
 Objective 3 – Be able to calculate wavelength, frequency, and
energy of light and understand the origin of the atomic emission
spectrum of an element.
 Objective 4 – Describe the different groups on the periodic table
and relate them to their electron configurations.
 Objective 5 – Interpret group and periodic trends in atomic radii,
ionic radii, ionization energies, and electronegativities.
The Atom Today
 Over time, the model of the atom evolved.
 Two early models we saw were:
 Thomson’s Plum Pudding Model
 Rutherford’s Nuclear Atom
The Atom Today
 The model proposed by Niel’s Bohr was the Planetary
Model
 The central nucleus (like the sun) surrounded by orbiting
electrons (like the planets)
 Explained that electrons don’t fall into nucleus because they
have fixed energy
 The Bohr model was an improvement, but was replaced by the…
Quantum Mechanical Model
 Modern model of the atom
 No longer are electrons treated like they travel like
“classical” particles (bowling balls)
 Focus is on electrons
 Electrons are found not in orbits but in “clouds”
 Based on probabilities
 Area where there is a 90% chance of finding an electron
 Electron clouds
 Are 3-dimensional
 Come in several shapes
 Are tied to specific energies
 Energy levels fill in special order
Organizing Electrons
Electrons in an atom are organized into
different energy levels
1. Principal energy levels have sublevels
2. Sublevels take the form of atomic orbitals
3. Orbitals “contain” electrons
Principal Energy Levels (n)
Principal energy levels (n) are numbered
Maximum number of electrons in a level is 2n2
n = 1
n = 2
n = 3
2 x 12 = 2 electrons
2 x 22 = 8 electrons
Each principal level has a number of sublevels
equal to the level number
n = 1
n = 2
1 sublevel
2 sublevels
Sublevels
Each sublevel contains a certain number
of atomic orbitals
Orbitals are regions where it is likely an electron
will be found
Each orbital can hold a maximum of 2 electrons
Letters are used to denote orbitals
Orbitals have characteristic shapes
Atomic Orbitals
Orbital
How many per Shape
sublevel?
s
1
spherical
p
3
peanut
d
5
4 are double-peanut
1 is a donut-ringed peanut
f
7
flower
Orbitals are regions in Space
The energy level of
an electron is the
region around the
nucleus where the
electron is likely to
be moving.
S orbital is a sphere
P orbitals

Each P orbital can hold two electrons, but they need
to have opposite spins
The P sublevel holds 6 electrons
D level orbitals
Each The D sublevel can hold 10 electrons.
Each orbital holds 2 electrons with opposite
spins
The F sublevel has 7
orbitals
Each orbital can hold
2 electrons with
opposite spin
The F sublevel holds
14 electrons
The F Sublevel
Atomic Orbitals
s
p
d
f
Electrons can change orbitals
 Electrons can change orbital, by
absorbing energy. When an
electron absorbs a quantum of
energy, it moves up to a higher
orbital.
 When the electron falls from a high
orbital to a lower orbital, energy is
released, and we see light.
Wintergreen mint is an example
We will also see this in our
spectroscopy and flame test
labs!
Atomic Orbitals
 Electron configurations
A series of numbers and letters to show which orbitals
contain electrons for a given element
 Before we proceed…
Aufbau Principle
 Electrons enter orbitals of the lowest energy first
Pauli Exclusion Principle
 No two electrons can have the same “state”
• State = electron’s orbital and its spin
• Electrons in the same orbital will have opposite spin
Hund’s Rule
 When electrons occupy orbitals of equal energy, one
electron enters each orbital until all orbitals contain one
electron with spin in the same direction