Transcript Slide 1
Friday, Nov. 2nd: “A” Day
Monday, Nov. 5th: “B” Day
Agenda
Finish Section 3.3: “Electron Configuration”
Quantum numbers, Pauli exclusion principle,
electron configuration, aufbau principle,
Hund’s rule
Electron Configuration Movie/Worksheet
Homework:
Electron Configuration Movie Worksheet
Quantum Numbers
Quantum number: a number that specifies the
properties of electrons
Each electron has 4 quantum numbers:
1. Principal quantum number, n:
The main energy level (row on periodic table)
2. Angular momentum quantum number, l:
The shape of the orbital (s, p, d, f)
3. Magnetic quantum number, m:
The orientation of the orbital around the nucleus
4. Spin quantum number, +½ or -½ (↑↓)
Pauli Exclusion Principle
Remember, each orbital can hold a maximum of
2 electrons.
In 1925 the German chemist Wolfgang Pauli
established a rule is known as the Pauli exclusion
principle.
Pauli exclusion principle: the principle that states
that two particles of a certain class cannot be in
the exact same energy state.
In plain English: no two electrons in the
same atom can have the same four
quantum numbers.
Electron Configuration
Electron configuration: the arrangement of
electrons in an atom.
Like all systems in nature, electrons in atoms
tend to assume arrangements that have the
lowest possible energies.
An electron configuration of an atom shows
the lowest-energy arrangement of the
electrons for the element.
Shapes of s, p, and d Orbitals
**Each Orbital Can Hold a Maximum
of 2 Electrons**
There is only 1 s orbital for each main energy level.
The s orbital can only hold 2 electrons.
There are 3 p orbitals for each main energy level.
The p orbitals can hold 2 electrons each for a total
of 6.
There are 5 d orbitals for each main energy level.
The d orbitals can hold 2 electrons each for a total
of 10.
There are 7 f orbitals for each main energy level.
The f orbitals can hold 2 electrons each for a total of
14.
An Electron Occupies the Lowest
Energy Level Available
Aufbau principle: the principle that states that
the structure of each successive element is
obtained by adding one proton to the nucleus of
the atom and one electron to the lowest-energy
orbital that is available.
In plain English: electrons occupy orbitals that
have the lowest energy first.
Orbital Filling Chart
This diagrams shows
how the energy of the
orbitals can overlap.
Because the 4s orbital
has a lower energy than
the 3d orbital, it will fill
first.
Hund’s Rule
Electron orbitals are filled according to Hund’s
Rule.
Hund’s rule: the rule that states that for an atom
in the ground state, the number of unpaired
electrons is the maximum possible and these
unpaired electrons have the same spin.
In plain English: all orbitals in a given energy
level must have 1 electron each before any
pairing occurs.
Don’t HOG electrons!
Writing Electron Configurations
There are 2 different ways that electron
configurations can be represented:
1. With arrows:
____ ____ ____ ____ ____
1s
2s
2p 2p
2p
Each horizontal line represents an orbital.
Each arrow represents an electron with a
different spin.
Which element do you think this this?
Writing Electron Configurations
2. With electron configuration notation:
1s22s22p5
The big numbers indicate the main energy
level, n (row on periodic table)
The letters indicate the orbital type.
The superscripts show the number of
electrons.
Which element do you think this this?
Electron Configuration Practice
Use arrows to write the electron configuration for
an atom of an element whose atomic number is 8.
Atomic Number = # of protons
# protons = # electrons = 8
Use the orbital filling chart to place the 8 electrons
in their proper orbitals.
Remember, the s orbital can only hold 2 electrons
and the 3 p orbitals can hold 2 electrons each for a
total of 6.
____ ____ ____ ____ ____
1s
2s
2p 2p
2p
Sample Problem C, pg. 98
Use arrows AND electron configuration notation to
write the electron configuration for an atom whose
atomic number is 20.
Atomic Number = # of protons
# protons = # electrons = 20
Use the orbital filling chart to place the 20
electrons in their proper orbitals:
__ ____ ____ ____ ____ ____ ____ ____ ____ ____
1s
2s
2p 2p 2p 3s
3p 3p 3p 4s
1s22s2sp63s23p64s2
Electron Configuration Practice
Use arrows AND electron configuration notation to
write the electron configuration for an atom that
has 17 electrons.
Use the orbital filling chart to place the 17
electrons in their proper orbitals:
____ ____ ____ ____ ____ ____ ____ ____ ____
1s 2s
2p 2p
2p
3s
3p 3p 3p
1s22s22p63s23p5
Movie:
“Writing Electron Configurations”
Welcome back Mr. Sweatervest!
Follow along and complete the student examples
as they are being discussed in the movie.
The rest of the worksheet,
front and back, is homework.
Homework
Complete the rest of the movie worksheet.
*Next time section 3.3 work day!*