The Periodic Table
|Characteristic |Pattern down a group |Pattern across a period |
|Atomic number and mass number |Increases |Increases |
|Atomic radius |Increases |Decreases |
|Melting points |Deceases for groups I to V and increases from groups |Gently increases then decreases |
| |V to VIII | |
|Reactivity |Metals become more reactive and non-metals become |Is high, then decreases and then increases. Group |
| |less reactive |VIII elements are inert and do not react. |
|Metallic character |Increases |Decreases |
The period table contains eight groups of elements; some have been given special, unique names.
• Group I elements are known as the alkali metals. The alkali metals all react strongly with water to form basic solutions.
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• Group II elements are referred to as the alkaline Earth Metals.
• Group VII elements are known as the halogens. The halogens are brightly coloured elements. Chlorine is green, bromine is red-brown and iodine is silvery-purple.
• Group VIII elements are known as the noble gases. The noble gases are inert and do not readily react with other substances.
• The block of elements in the middle of the table is known as the transition metal blocks.
The line that zigzags through the periodic table separates the metals from the non-metals. About three-quarters of all elements are classified as metals. The metals are found on the left-hand side of the table. Eight elements that fall along this line have properties belonging to both metals and non-metals. They are called metalloids.
The periodic table includes the names, symbols and atomic numbers of most of the known elements. The symbols are a form of short-hand for writing the names of the elements and are recognises Worldwide. Some periodic tables describe the properties of each element, including its physical state at room temperature, melting point, boiling point and relative atomic mass. Most elements exist as solids under normal conditions and a few exist as gases. Only two elements exist as liquids at normal room temperature and pressure.