Elements

1. Elements form the simplest basic unit of matter.
2. An element is a substance that contains atoms of only one type. An element cannot be broken into two or more simpler substances by any chemical method.
3. Air and water, the most common substances are not elements as they are made of more than one type of element.
4. There are around 106 elements and these are grouped and classified systematically according to their properties. This results in The Periodic Table.
5. Periodic Table is a ready reckon-er chart where elements are arranged according to their atomic number (ie) number of protons in the nuclei.
6. Each element is given a symbol, with its atomic number written near it.
   (eg) Nitrogen is represented by the symbol N, in the periodic table.
7. The vertical column (top to bottom) in the periodic table is the group. Elements in a group share similar chemical properties.(eg) Helium, Neon, Argon, Krypton, Xenon and Radon
8. Each horizontal row in the table is called a period. Properties of elements in a period change gradually from metallic to non-metallic, as we move from left to right.
9. The elements on the left side of the periodic table are mainly metals, while those on the right are non-metals. For example in period ll, elements Boron, Carbon, Nitrogen are non-metals.
10. The zig-zag line separates the metals from non-metals.