1. The horizontal rows is called the PERIOD.
2. There are 7 periods in period table.
3. The first period only has 2 elements only.
4. The second and third period consist of 8 elements, are called the short period.
5. The forth and the fifth period consist of 18 elements, are called the long period.
6. The sixth and the seventh period has 32 elements.

Classification of Elements in a Periodic Table
Chemistry Form 4 kssm Chapter 4 - The Periodic Table of Elements

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