The current atomic theory is called the Standard Model: • Protons & neutrons in the nucleus- made of quarks • Nucleus is small, dense & held together by strong nuclear force • Electrons in the electron cloud- divided up into energy levels • Electrons behave like waves & change locations by absorbing or releasing packets of energy in the form of electromagnetic waves.
Orbitals • Electrons are located in orbitals, regions within specific energy levels around a nucleus. • Orbitals are regions where electrons are likely to be found.
s Orbital ( 1 type)
p Orbital ( 3 types)
f Orbital ( 7 types)
d Orbital ( 5 types)
How are the orbitals distributed in the electron cloud?
Orbitals by Energy Level
Energy level 1 has a single s orbital Energy level 2 has one s orbital and three p orbitals Energy level 3 has one s orbital, three p orbitals and five d orbitals Energy level 4 has one s orbital, three p orbitals, five d orbitals and seven f orbitals
Orbitals by Energy Level
Energy level 5 has one s orbital, three p orbitals, five d orbitals, seven f orbitals and nine g orbitals. Energy level 6 has one s orbital, three p orbitals, five d orbitals, seven f orbitals, nine g orbitals and 11 h orbitals. Each orbital holds 2 electrons.
What are electron configurations?
Electron Configurations
The ways in which electrons are arranged in various orbitals in the electron cloud are called electron configurations. Three rules—the aufbau principle, the Pauli exclusion principle, and Hund’s rule—tell you how to find the electron configurations of atoms.
What determines the order of filling orbitals?
Electron Configurations
According to the aufbau principle, electrons occupy the orbitals of lowest energy first.
The aufbau diagram shows the relative energy levels of the various atomic orbitals. Orbitals of greater energy are higher on the diagram.
Electron Configurations
Aufbau Diagram 6p 5d
6s
5p 4d
5s
Increasing energy
4p 4s
3d 3p
3s 2p
2s
1s
Each box represents an atomic orbital.
4f
An electron occupies the lowest energy orbital available
So, the order in which the orbitals are filled matches the order of increasing energies. 1s → 2s → 2p → 3s → 3p → 4s → 3d → 4p → 5s → 4d → 5p → 6s → 4f → 5d → 6p → 7s → 5f → 6d → 7p
How many electrons are in each orbital?
Electron Configurations
According to the Pauli exclusion principle, an atomic orbital holds at most two electrons.
To occupy the same orbital, two electrons must have opposite spins. A vertical arrow indicates an electron and its direction of spin ( or ). An orbital containing paired electrons is written as .
What happens if there are not enough electrons to fill an orbital?
Electron Configurations
According to Hund’s rule, every orbital in a subshell is singly occupied with one electron before any one orbital is doubly occupied, and all electrons in singly occupied orbitals have the same spin. Example: The 4th energy level has three p orbitals. Each 4p orbital gets one electron before any 4p orbital gets two.
What are the ways to write electron configuration?
Electron Configurations
1.Orbital Diagram:
sulfur-
1s
2s
2p
2p
2p
3s
3p
3p
3p
2. Standard Electron Configuration: sulfur- 1s2 2s2 2p6 3s2 3p4
3. Noble Gas (Shorthand) Configuration: sulfur- [Ne] 3s2 3p4
How are orbital diagrams written?
Orbital Diagrams
1.Find the number of electrons in the element. Ti= 22 electrons 2. Make a blank orbital diagram chart. 1s
2s
2p
2p
2p
3s
3p
Make sure you follow the Affbau diagram to put the orbitals in the correct order.
3p
3p
4s
3d
3d
3d
3d
3d
Orbital Diagrams
3. Fill in the correct number of arrows for that element: Ti= 22 electrons 1s 2s 2p 2p 2p 3s 3p 3p 3p 4s 3d 3d 3d 3d 3d
Remember: Electrons do not pair up within an orbital subshell until every orbital has one up arrow.
How are standard electron configurations written?
Electron Configuration
1.Find the number of electrons in the element. Br= 35 electrons 2. Use the Order of Filling Electron Orbitals chart to determine the correct order to write.
1s 2s 3s 4s 5s 6s 7s
Start at the top arrow and go down each row.
2p 3p 4p 5p 6p 7p
3d 4d 4f 5d 5f 6d
Electron Configuration
3. Write the orbital then the number of electrons in that orbital as an exponent until you run out of electrons. Br= 35 electrons
1s 2s 3s 4s 5s 6s 7s
2p 3p 4p 5p 6p 7p
3d 4d 4f 5d 5f 6d
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5 The exponents should add up to 35.
How are noble gas electron configurations written?
Noble Gas Configuration
1. Find the number of electrons in the element. Sr= 38 electrons 2. Find the noble gas (group 18) element in the period directly above it. Kr= 36 electrons
Noble Gas Configuration
3. Use the noble gas symbol in brackets
[ ] to replace the section of the electron configuration equal to the number of electrons in the noble gas. strontium- [Kr] 5s2
