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The Periodic Law – Chapter 5
What does the word “periodic”
mean?
• Periodic:
Mendeleev 1869
• Arranged elements according to
_______________________
• Put elements of similar properties in the
same_______________________
• Why did he leave blank spots in table?
2 questions …..
1. Why could most elements be arranged in
order of increasing atomic mass but a few
could not? (Te & I, Co & Ni, Ar & K)
2. What was the REASON for chemical
periodicity?
Henry Mosley
1911 (40+ years later)…
• Used X-ray and spectral studies to show
that each element has ________________
• ___________________ is a better basis for
organizing the Periodic Table
Periodic Law
• The physical and chemical
properties of the elements are
periodic functions of
their___________
Modern Periodic Table
• An arrangement of the elements in
order of their______________
so that elements with similar properties
fall in the same___________,
or _____________
Noble Gases
• Proposed by Sir William Ramsay and John
William Strutt
• Lack of chemical ______________
The Lanthanides
• The 14 elements with atomic numbers from
58(cerium, Ce) to 71(lutetium, Lr)
• Similar in__________ and___________
properties
The Actinides
• The 14 elements with atomic number from
90(thorium, Th) to 103(lawrencium, Lr)
Periodicity
• Figure 5-4 on page 126
• Periodicity is explained by the arrangement
of the________________around the
nucleus
5-2
Electron Configuration and
The Periodic Table
What is the outer configuration
of the following:
• Re (#75)
• I (#53)
• Cd (#48)
Which sublevel fills in after the…
• 4s
• 4d
• 6s
• 5p
5-3
Electron Configurations and
Periodic Properties
Atomic Radius
• One-half the distance between the nuclei
of identical atoms that are bonded together
Group Trend for Atomic Radii
• Down a group the radius of an atom gets
……..…. because…
Period Trend for Atomic Radii
• Across a period the radius of an atom gets
………………....because….
• Exception: Noble Gas Family – atoms don’t interact
and pull together like in other atoms because__
Why does the atomic radii not
decrease very much as you move
across the d-sublevel?
Why would the atomic radius of
hafnium (#72) be LESS than that
of zirconium (#40)?
Ionization energy, IE
• Energy required to _________ an electron
from a neutral atom (or first ionization
energy, IE1)
• __________: charged particle
• _______________: process of an electron
being lost or gained from an atom which
results in the formation of an ion
Group Trend for Ionization Energies
• Down a group the ionization energy of
an atom generally gets …………………
because….
Period Trend for Ionization
Energies
• Across a period the ionization
energy …….…..because
4 Factors Affecting Ionization
Energy
Multiple Ionization Energies
• Energy required to remove the 2nd, 3rd,
etc. electron from an atom
• IE3……. IE2….. IE1 because ………
Why does the IE go UP as you go
down a d-sublevel group but go
down in an s sublevel?
Electron Affinity p. 147
• Energy change the occurs when an _______
___________________ by a neutral atom
• Most atoms _______ energy when they acquire an
electron: A + e-  A- + energy
– energy has _____sign
• Some atoms ________ energy when they acquire an
electron: A + e- + energy  A– energy has ______ sign; atom is unstable &
loses electron spontaneously
Group Trend for Electron Affinities
• Down a group the electron affinity of an
atom tends to get …………….because
Period Trend for Electron Affinity
• Across the p-sublevel, the energy change
………………(becomes more …………..)
because…..
Why is the electron affinity of
nitrogen so low when compared
to carbon or oxygen?
Multiple Electron Affinities
• It is always ……………….. to add a 2nd
electron to an already negatively charged
ion..therefore, all 2nd electron affinities
are …………………..
Ionic Radii
• Cation:
• _________ ion
• Formed by an atom ………….
electron(s)
• Always …………. because electron
cloud is smaller (less repulsion) &
sometimes even one less energy level!
• Anion:
• __________ ion
• Formed by an atom ……………
electron(s)
• Always …………. because electron cloud
is greater (more repulsion among
electrons)
Group Trend for Ionic Radii
• Down a group the ionic radius of an
atom generally gets ……………because
.
Period Trend for Ionic Radii
• Metals (left side):form …………….
– Cationic Radius: ………….. ionic radius
as nuclear charge increases without adding
an energy level
• Non-metals: form ………………
– Anionic Radius:……………………. ionic
radius as nuclear charge increases without
adding an energy level
Valence Electrons
• Electrons available to be lost, gained, or
shared in the formation of chemical
compounds
• Often the outermost electrons because they
are held most loosely
What would be the # of valence
electrons in……..
•
•
•
•
Calcium
Lithium
Chlorine
carbon
What would be the # of valence
electrons in……..
•
•
•
•
Calcium – 2 : 4s2
Lithium – 1: 2s1
Chlorine – 7: 3s23p5
Carbon – 4: 2s22p2
Electronegativity
• Measure of the ability of an atom ______
___________________to attract electrons
• ___________________ is the MOST
electronegative element – assigned an
arbitrary value of ______
• All other values are relative to F
• 3 highest values: F – O - N
Group Trend for Electronegativity
• Tend to ___________ down a group
(or stay the same) as the atoms gets
larger
Period Trend for Electronegativity
• Tend to _______________ across the
period as the atoms gets ________, the
nuclear charge becomes ___________,
and the atom is getting closer to a
noble gas configuration
Determine the likely charge for the
following elements: Ca, O, Al
1. Write the noble gas configuration of the
element
2. Determine if electrons will be LOST or
GAINED to make the element stable
3. ID the noble gas whose electron
configuration by losing/gaining these
electrons
4. Write the formula for the ion
5. ID it as a cation anion
How do d-block elements form
ions?
• Electrons in the highest occupied
sublevel are always removed first
Why does zinc become a +2 ion?
Which electrons are lost when titanium
becomes a +2, a +3 and a +4 ion?