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The Periodic Table
What does the Group
Number and Period
tell you about the Electrons of an Element?
Why is the Group Number of an Element important?
number of an element in the periodic table
is the same as the number of electrons in its outer shell.
An element in group
1 has 1 electron in its outer
An element in group 2 has 2 electrons in its outer shell.
An element in group 7 has 7 electrons in its outer shell.
An element in group 0 has a full outer shell.
The number of electrons in the outer shell gives the
its chemical properties and controls its chemical reactions.
Why is the Period of an Element important?
(row) in which an element is found
number of electron shells that it has.
The first period contains only hydrogen and helium.
Hydrogen and helium have only 1 electron shell.
The second period is from lithium to neon.
These elements have 2 electron shells.
The third period is from sodium
These elements have 3 electron shells and so on.
What is the Electron Structure of an Element?
We can write the electron structure
of an element
according to the total number of electrons in its shells.
The inner shells are always full and have the numbers 2, 8, 8, 18.
For example, a potassium
atom has the
electron structure 2, 8, 8, 1.
Potassium is an alkali metal. See a picture of a potassium atom.
It is in group 1 (1 electron in its outer shell) and period 4 (4 shells).
A chlorine atom has the electron
structure 2, 8,
Chlorine is a halogen. See a picture of a chlorine atom. Chlorine
is in group 7 (7 electrons in its outer shell) and period 3 (3 shells).
The electron structure is also called the electronic structure,
the electron configuration or the electronic configuration.
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