CHAPTER 7
Electronic Structure
and Periodicity
CHAPTER 7.2 ELECTRON CONFIGURATION
MELC:
Write the electron configuration of
atoms [STEM_GC11ES-IIa-b-56]
CHAPTER 7.2 ELECTRON CONFIGURATION
Electron Configuration
- the electron configuration of an
atom is a representation of its
arrangement and distribution.
CHAPTER 7.2 ELECTRON CONFIGURATION
A simple way to show the
arrangement of electrons around an
atom is to arrange the electrons in
energy levels or shells around the
nucleus of an atom.
CHAPTER 7.2 ELECTRON CONFIGURATION
Electrons that are closest to the
nucleus, or those occupying the first
energy level, have the lowest energy.
Electrons that are farther away from the
nucleus have higher energy.
CHAPTER 7.2 ELECTRON CONFIGURATION
The paths that electrons take
as they circle around the nucleus of
an atom are called orbitals or
subshells.
CHAPTER 7.2 ELECTRON CONFIGURATION
There are four different orbital shapes:
s – sharp
p – principal
d – diffuse
f - fundamental
CHAPTER 7.2 ELECTRON CONFIGURATION
https://i.stack.imgur.com/i8V5L.png
CHAPTER 7.2 ELECTRON CONFIGURATION
Guidelines in determining the
electron configuration of an element:
• An orbital can hold only two electrons.
Electrons that occupy the same orbital
are called an electron pair.
CHAPTER 7.2 ELECTRON CONFIGURATION
• An electron will always enter the orbital with the
lowest energy level.
• An electron can occupy an orbital singly, but it
should occupy a lower-energy orbital with
another electron before occupying a higher-
energy orbital. In other words, within an energy
level, electrons will fill an s orbital first before
filling the p orbitals.
CHAPTER 7.2 ELECTRON CONFIGURATION
• The s subshell can hold
2 electrons; the p
subshell can hold 6
electrons; the d subshell
can hold 10 electrons;
and the f subshell can
hold 14 electrons.
CHAPTER 7.2 ELECTRON CONFIGURATION
RULES FOR ASSIGNING ORBITALS
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p
CHAPTER 7.2 ELECTRON CONFIGURATION
Hund’s Rule
When assigning electrons to orbitals, each
electron will first fill all the orbitals with the
same energy or degenerate orbitals before
pairing with another electron. Atoms at ground
state tend to have as many unpaired electrons
as possible.
CHAPTER 7.2 ELECTRON CONFIGURATION
Hund’s rule is also often called “the empty
bus seat rule.” think about how electrons fill
orbitals like most people do on seats of an empty
bus. A passenger would not sit next to a total
stranger if there are still empty rows available. Only
after all the seats are taken would a passenger sit
next to someone or pair up.
CHAPTER 7.2 ELECTRON CONFIGURATION
The Aufbau Principle
It is derived from the German word aufbauen,
which means “to build.” Electron configurations are
written in such a way that orbitals are built up from
atom to atom. In writing the electron configuration of an
atom, orbitals are filled in order of increasing atomic
number.
CHAPTER 7.2 ELECTRON CONFIGURATION
CHAPTER 7.2 ELECTRON CONFIGURATION
Exceptions
The Aufbau principle predicts the electron
configuration of most elements. However, there are
exceptions among the transition metals and heavier
elements. These exceptions occur because some
elements are more stable if the subshells are half-
filled or fully-filled.
CHAPTER 7.2 ELECTRON CONFIGURATION
Examples:
Element Expected Observed
Cr (Z = 24) [Ar] 3d4 4s2 [Ar] 3d5 4s1
Cu (Z = 29) [Ar] 3d9 4s2 [Ar] 3d10 4s1
CHAPTER 7.2 ELECTRON CONFIGURATION
CHAPTER 7.2 ELECTRON CONFIGURATION
Writing Electron Configurations
1. Write the energy level (the period)
2. Write the subshell to be filled
3. Write the superscript – the number of
electrons in that subshell.
CHAPTER 7.2 ELECTRON CONFIGURATION
Orbital Diagram
- a representation of electron
configuration by which each of the
separate orbitals and the spins of the
electrons are shown.
CHAPTER 7.2 ELECTRON CONFIGURATION
CHAPTER 7.2 ELECTRON CONFIGURATION
CHAPTER 7.2 ELECTRON CONFIGURATION
spdf Notation
CHAPTER 7.2 ELECTRON CONFIGURATION
Noble Gas Notation
Noble gases, which are also known as inert gases,
have the most stable electron configurations. Because
noble gases have their subshells filled, they can be used
as a simpler way of writing electron configurations for
succeeding elements. The noble gas above the element is
used to represent the subshells that have been filled.
Then, the valence electrons in the outermost shells are
written.
CHAPTER 7.2 ELECTRON CONFIGURATION
CHAPTER 7.2 ELECTRON CONFIGURATION
Magnetism Properties
Magnetism is a physical phenomenon produced
by the motion of electric charges. This can result in
attraction or repulsion, depending on the force
between the atoms.
Magnetism can result from the unpaired electrons
of an element. As electrons spin, they produce a
magnetic field
CHAPTER 7.2 ELECTRON CONFIGURATION
Paramagnetism
- it is the magnetic state of an atom with one or
more unpaired electrons.
Diamagnetism
- it is the magnetic state wherein an atom has no
unpaired electrons.
CHAPTER 7.2 ELECTRON CONFIGURATION
