Which of the following statement about the modern periodic table is correct?

Options

A. It has 7 vertical columns known as periods
B. It has 8 horizontal rows known as groups
C. It has 18 vertical columns known as groups
D. It has 9 horizontal rows known as periods

Explanation

To determine which statement about the modern periodic table is correct, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding the Structure of the Modern Periodic Table**:
- The modern periodic table is organized based on atomic number, which is the number of protons in an atom's nucleus. This organization reflects the periodicity of elements' physical and chemical properties.

2. **Evaluating Each Option**:
- **Option A**: "It has 7 vertical columns known as period."
- This statement is incorrect. The vertical columns in the periodic table are called "groups," not periods.

- **Option B**: "It has 8 horizontal rows known as group."
- This statement is also incorrect. The horizontal rows in the periodic table are called "periods," not groups.

- **Option C**: "It has 18 vertical columns known as group."
- This statement is correct. The modern periodic table consists of 18 vertical columns, which are referred to as "groups."

- **Option D**: "It has 9 horizontal rows known as period."
- This statement is incorrect. The modern periodic table has 7 horizontal rows, known as "periods."

3. **Conclusion**:
- After evaluating all the options, we find that **Option C** is the correct statement regarding the modern periodic table.

### Final Answer:
**The correct statement about the modern periodic table is: Option C - it has 18 vertical columns known as group.**

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