The Periodic Table
The periodic table, as we know it today, is an array of the elements
arranged in order of increasing atomic number.
When the elements are arranged in order of increasing atomic number, the physical and chemical properties
of the elements vary periodically at regular intervals. This relationship
is known as the
periodic law.
(i) Periods
Use the button bar down below to view the periodic table as we know it today. Click on the symbols on the periodic
table to find out the element's name, its atomic number and its atomic mass.
Check out this site to learn about the early periodic table.
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The number of the period gives the number of the outermost principal energy level that the valence electron(s) occupies. This is best illustrated by reviewing the arrangement of electrons in principal energy levels and the Bohr diagrams.
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There are 18 vertical columns of elements in the periodic table. Each column is called a group of elements, or a family of elements. Elements in the same family tend to have similar properties.
There are two formats in labelling the groups on the periodic table. In some books (and on the Internet) you will find the "1-18" numbering sequence. In other books, you will find the more popular "1-8 A and B" group labelling system. In this course, we will use the latter system of labelling.
Learn the names associated with the Groups of Elements.
| "A" elements | Elements |
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| Group IA | Alkali metals | ||
| Group IIA | Alkaline earth metals | ||
| Group VIIA | Halogens | ||
| Group VIIIA | Noble gases
| "B" elements |
The Transition Elements | |
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Metals, Nonmetals and Semimetals
Do you know where to locate:
Metals have a tendency of forming cations.
The bonding of atoms in metals is referred to as
metallic bonds.
(ii) Ionic Bond
When metals on the left-hand-side of the periodic table react with
nonmetallic elements on the right-hand-side of the periodic table to form
compounds, these compounds are held together by
ionic bonds.
(iii) Covalent Bond
The chemical bonds formed by sharing of electrons between non-metallic
elements are referred to as covalent bonds .
Examples are:
These seven elements exist as diatomic
molecules are the diatomic elements.
Take a look at
how the periodic table organizes these classes of elements.
(i) Metallic Bond
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| A metal ion has a radius that is approximately half that of the corresponding metal atom |
| An anion is approximately twice that of the corresponding nonmetal atom. |
| For isoelectronic ions, the radius decreases as the positive nuclear charge increases. |
The melting point and boiling point are measures of the attractive forces between atoms or molecules. Elements, such as metals, that have strong attractive forces have higher melting points and boiling points than nonmetals, which have very weak forces of attraction.
(i)The Halogens
The physical states of the halogens at room temperature varies from gas to liquid to solid as one moves down the group. As a result, the melting points and boiling points increase as one moves down the group.
(ii)The Alkali Metals
The alkali metals show a decrease in melting points and boiling points due to the weaker metallic bonds between atoms as their size increase down the group.
The metallic elements are found on the left-hand-side of the periodic table.
The non-metallic elements are found on the right-hand-side of the periodic table.
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All contents copyrighted © 1997 Rosamaría Fong, Instructor of Chemistry All Rights reserved