Chapter: 3 PeriodicityTitle: Lesson 1 The Periodic Table
Learning Objectives:
• Reflect on prior knowledge of the periodic table• Understand the structure and purpose of the periodic table• Repeat the work of Mendeleev by constructing your own periodic table
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Janet Periodic TableElements arranged in order of orbital filling. Used frequently by physicists.
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The periodic table and electron configuration
How does an element’s position in the PT relate to its electron configuration?
THE MODERN PERIODIC TABLE
occur in the same vertical columns (GROUPS).
= the elements arranged in rows (PERIODS)
such that chemically similar elements
in order of increasing atomic number (Z)
Period 1
Period 2
Period 3
Period 4
Period 5
Period 6
Period 7
Gro
up
1 G
rou
p
2 Gro
up
3 G
rou
p
4 Gro
up
5 G
rou
p
6 Gro
up
7 G
rou
p
0
Transition Elements
Group VII
GROUP
Group number =number of electrons in highest occupied energy level
e.g. Group I the alkali metals
the halogens
eg Na[2,8,1] =
eg F[2,7] =
= elements within the same vertical column
Chemical and physical properties are similar within a group
PERIOD
Chemical and physical properties change from extremes across any period.
e.g. Period 3
Sodium= a reactive metallic solid
Argon= an unreactive, non- metallic gas
eg Si (Z=14)
Period number =number of energy levels
2,8,4 Period 3 and Group 4
= elements within the same horizontal row
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Groups and Periods - Summary
Groups Elements show similar chemical properties Elements show similar trends in their chemical
properties
Periods As you move across periods, changes in the
chemical and physical properties that are repeated in the next period
This is what ‘period’ and ‘periodic’ refers to
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Key Points
The periodic table arranges the elements according to:
Their chemical properties
Their electronic structure
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Elements whose valence electrons that occupy an s sub level make up the s block.
The same can be said with p block, d block and f block elements.
E.g. Sodium:• Period 3 (3 principal energy levels)• Group 1 (one electron in the valence energy level {Ne} 3s1.
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Metals and Non Metals Metals, non metals and metalloids occupy
different regions of the PT.
Metalloids have the characteristics of both metals and non-metals.
The physical properties and appearance most resemble the metals, although chemically they are more like non metals.
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Metallic properties A metallic structure consists of a regular
lattice of positive ions and a sea of delocalised electrons.
To form metallic structure, an element must be able to lose electrons to form positive ions.
Going across a period means an increase of ionisation energy (thus less easy to lose electrons)
Metallic structures are formed by elements on the left hand side because of the lower ionisation energy.
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The periodic table and electron configurations
Electrons in the outer shell are called valence electrons.
The group number is related to the number of valence electrons.
For elements in groups 13-18, the number of valence electrons is given by: GROUP NUMBER – 10
Periodic table divided into s, p, d and f blocks.
E.g. Sulphur: Period 3, group 16, p block.
So we know… 3 shells, (16-10) valence electrons, highest energy shell is
a p sub shell.
What is the outer shell electron configuration?
3s23p4 (six valence electrons)
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Being Mendeleev
The first widely accepted periodic table was produced by the Russian chemist Dmitri Mendeleev
It was a tremendous example of scientists as risk-takers as it was able to make a number of predictions thought unlikely at the time
Complete the exercise here in which you will use the information available to Mendeleev to construct your own periodic table