In the modified mendelev 's periodic tables ___________groups and _________periods are present whereas in modern periodic table _____

Answer

To answer the question regarding the number of groups and periods in the modified Mendeleev's periodic table compared to the modern periodic table, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Structure of Mendeleev's Periodic Table:**
- Mendeleev's periodic table was organized based on atomic mass.
- It consists of horizontal rows called periods and vertical columns called groups.

2. **Count the Number of Groups and Periods in Mendeleev's Table:**
- Mendeleev's periodic table has **8 groups** and **7 periods**.

3. **Identify the Structure of the Modern Periodic Table:**
- The modern periodic table, developed by Moseley, is organized based on atomic number.
- It also consists of periods and groups.

4. **Count the Number of Groups and Periods in the Modern Table:**
- The modern periodic table has **18 groups** and **7 periods**.

5. **Formulate the Final Answer:**
- In the modified Mendeleev's periodic table, there are **8 groups** and **7 periods**, whereas in the modern periodic table, there are **18 groups** and **7 periods**.

### Final Answer:
In the modified Mendeleev's periodic table, **8 groups** and **7 periods** are present, whereas in the modern periodic table, **18 groups** and **7 periods** are present.