ICSE Class 9 Answered

Essential features of Mendeleev’s Periodic Table

1. There are eight vertical columns called groups. They are numbered from I to VIII. Groups I to VII are further divided into two subgroups A and B.
2. All the elements of a sub-group have similar properties and show same valency, which is equal to the group number.
3. There are seven horizontal rows, known as periods. They are numbered from 1 to 7. As one moves from left to right in a period, there is a gradual change from metallic to non-metallic properties.