Modern Periodic Law and the Structure of the Periodic Table

The Modern Periodic Law states:  

“The physical and chemical properties of elements are periodic functions of their atomic numbers.”

In simple terms, when elements are arranged in order of increasing atomic numbers, those with similar properties reappear at regular intervals. This repetition is a direct consequence of the periodic variation in their electronic configurations.

The Long Form of the Modern Periodic Table

Today’s periodic table is the most refined version, organizing all 118 known elements into a logical framework:

- Periods (Horizontal Rows): 7 in total  

- Groups/Families (Vertical Columns): 18 in total  

- Blocks: 4 (s, p, d, f), based on the type of orbital being filled  

Number of Elements in Each Period

- Period 1 → 2 elements  

- Period 2 → 8 elements  

- Period 3 → 8 elements  

- Period 4 → 18 elements  

- Period 5 → 18 elements  

- Period 6 → 32 elements  

- Period 7 → 32 elements  

Formula for Elements in a Period

Number of elements = 2 [Int((N+2)/2)]^2

Where:  

- N = period number  

- Int(x) = integer value (rounding down)  

This formula helps predict how many elements will appear in each period.