SCH4U Exam Study Notes
Compiled SCH4U Course Review
Unit 1: Atomic Structure and Bonding
Section 3.3
Electron Configurations and Periodic Trends (pg. 139-157)
Feb. 11
For single electron system all orbitals with the same value of have the same energy
Atoms with more than 1 electron with the same value of n have different energies (sublevels)
Because of interactions between additional electrons
All orbitals within a sublevel have the same energy
The Fourth Quantum Number: A property of the electron (spin quantum number: ms)
Describes property of the electron that results from a particle like nature
Electrons can spin in one of two directions (each direction generates a magnetic field)
Two possible values that specify direction electron is spinning
Pauli Exclusion Principle: only 2 electrons of opposite spin can occupy an orbital (an orbital can have a max of 2 electrons with opposite spins)
Orbital can also have only 1 electron or 0 electrons
No 2 electrons in an atom can have the same 4 quantum numbers
Summary: (4 quantum numbers)
Electron Configurations:
Electron configuration: notation that shows number and arrangement of electrons in its orbitals
Infinite number of electron configurations because infinite values of n
For each atom, all but one of these represents the atom in an excited state
Atom’s chemical property mainly associated with its ground state electron configuration
Unless otherwise stated, assume electron configuration is in its ground state
Ex: 1s2 (superscript represents 2 electrons in s orbital)
Aufbau principle: process of building up the ground state electronic structure for atoms (in order of atomic #)
Writing electron Configurations:
Provide info about first 2 quantum numbers (n and l)
Ex: boron in ground state:
Orbital diagram: boxes are used for each orbital
Empty box represents an orbital with no electrons, box with single upward or downward pointing arrow represents 1 electron, box with 2 oppositely
Unit 1: Atomic Structure and Bonding
Section 3.3
Electron Configurations and Periodic Trends (pg. 139-157)
Feb. 11
For single electron system all orbitals with the same value of have the same energy
Atoms with more than 1 electron with the same value of n have different energies (sublevels)
Because of interactions between additional electrons
All orbitals within a sublevel have the same energy
The Fourth Quantum Number: A property of the electron (spin quantum number: ms)
Describes property of the electron that results from a particle like nature
Electrons can spin in one of two directions (each direction generates a magnetic field)
Two possible values that specify direction electron is spinning
Pauli Exclusion Principle: only 2 electrons of opposite spin can occupy an orbital (an orbital can have a max of 2 electrons with opposite spins)
Orbital can also have only 1 electron or 0 electrons
No 2 electrons in an atom can have the same 4 quantum numbers
Summary: (4 quantum numbers)
Electron Configurations:
Electron configuration: notation that shows number and arrangement of electrons in its orbitals
Infinite number of electron configurations because infinite values of n
For each atom, all but one of these represents the atom in an excited state
Atom’s chemical property mainly associated with its ground state electron configuration
Unless otherwise stated, assume electron configuration is in its ground state
Ex: 1s2 (superscript represents 2 electrons in s orbital)
Aufbau principle: process of building up the ground state electronic structure for atoms (in order of atomic #)
Writing electron Configurations:
Provide info about first 2 quantum numbers (n and l)
Ex: boron in ground state:
Orbital diagram: boxes are used for each orbital
Empty box represents an orbital with no electrons, box with single upward or downward pointing arrow represents 1 electron, box with 2 oppositely