Electron Configurations Electron configurations show the arrangement of electrons in an atom. A...
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Electron Configurations Electron configurations show the arrangement of electrons in an atom. A distinct electron configuration exists for atoms of each
Electron Configurations Electron configurations show the
arrangement of electrons in an atom. A distinct electron
configuration exists for atoms of each element. Electrons like to
assume arrangements that have the lowest possible energies.
Slide 3
Rules Governing Electron Configurations To build up electron
configurations for the ground state of any particular atom, first
the energy levels of the orbitals are determined. Then electrons
are added to the orbitals one by one according to three basic
rules.
Slide 4
Aufbau Principle an electron occupies the lowest energy orbital
that can receive it.
Slide 5
Pauli Exclusion Principle no two electrons in the same atom can
have the same set of four quantum numbers. According to the Pauli
exclusion principle, an orbital can hold two electrons of opposite
spin states. In this electron configuration of a helium atom, each
arrow represents one of the atoms two electrons. The direction of
the arrow indicates the electrons spin state.
Slide 6
Hunds Rule orbitals of equal energy are each occupied by one
electron before any orbital is occupied by a second electron, and
all electrons in singly occupied orbitals must have the same spin.
The figure shows how (a) two, (b) three, and (c) four electrons
fill the p sublevel of a given main energy level according to Hunds
Rule. (a)(b) (c)
Slide 7
Representing Electron Configurations Orbital Notation an
unoccupied orbital is represented by a line _____, with the
orbitals name underneath. Arrows represent electrons. Berylliums
orbital notation would be 1s2s Beryllium has four electrons which
are represented by four arrows in the orbital notation above.
Slide 8
Representing Electron Configurations Electron Configuration
Notation eliminates lines and arrows. Heliums configuration is 1s
2. 1s 2 Helium The superscript indicates that there are two
electrons in heliums 1s orbital. 1s 2 2s 2 2p 3 Nitrogen How many
electrons are present in a nitrogen atom? The number of electrons
in a nitrogen atom is equal to the sum of the superscripts in its
electron configuration notation: 2 + 2 + 3 = 7 electrons.
Slide 9
Noble Gas Notation Compare the configuration of a sodium atom
with that of an atom of neon. Sodium, Na1s 2 2s 2 2p 6 3s 1 Neon,
Ne 1s 2 2s 2 2p 6 Notice that the first 10 electrons in a sodium
atom have the same configuration as a neon atom. This similarity
allows us to use a shorthand notation for the electron
configuration of sodium. [Ne]3s 1
Slide 10
Representing Electron Configurations Noble Gas Notation used to
simplify electron configurations. [Ne]3s 1 would be the electron
configuration for sodium. A noble gas configuration is an outer
main energy level fully occupied, in most cases by eight electrons.
To simplify sodiums notation, the symbol for neon, enclosed in
square brackets, is used to represent the complete neon
configuration: [Ne] = 1s 2 2s 2 2p 6. This allows us to write
sodiums configuration as [Ne]3s 1.
Slide 11
Exceptions Electron configurations of some atom, such as
chromium and copper, deviate from the predictions of the Aufbau
principle, but the ground-state configuration that results is the
configuration with the minimum possible energy.
Slide 12
Create a Foldable Create a foldable to explain the three rules
of electron configurations Be sure to include: 1.Aufbau Principle
2.Pauli Exclusion Principle 3.Hunds rule Use words and
illustrations Be as detailed as possible