The base of modern periodic table is

Options

A. atomic weight
B. atomic number
C. atomic volume
D. atomic energy

Explanation

To determine the base of the modern periodic table, let's analyze the options given:

1. **Atomic Weight**: Historically, earlier periodic tables were organized based on atomic weights. However, this approach led to inconsistencies and anomalies in the arrangement of elements.

2. **Atomic Number**: The modern periodic table is primarily organized by atomic number, which is the number of protons in the nucleus of an atom. This arrangement reflects the periodic law, which states that the properties of elements are a periodic function of their atomic numbers.

3. **Atomic Volume**: While atomic volume can show trends across the periodic table, it is not the foundational basis for the arrangement of elements.

4. **Atomic Energy**: This term is not commonly used in the context of the periodic table and does not serve as a basis for its organization.

Based on this analysis, the correct answer is:

**The base of the modern periodic table is atomic number.**

### Step-by-Step Solution:
1. **Identify the options**: The options provided are atomic weight, atomic number, atomic volume, and atomic energy.
- Hint: Consider the historical context of how elements were organized in earlier periodic tables.

2. **Evaluate atomic weight**: Recognize that atomic weight was used in earlier models but led to inconsistencies.
- Hint: Think about why scientists moved away from using atomic weight as a basis.

3. **Assess atomic number**: Understand that the modern periodic table is organized by atomic number, which correlates with the number of protons in an atom.
- Hint: Recall the definition of atomic number and its significance in determining element properties.

4. **Consider atomic volume and atomic energy**: Acknowledge that these options do not serve as the foundational basis for the periodic table.
- Hint: Reflect on how these concepts relate to the properties of elements but do not define their arrangement.

5. **Conclude with the correct answer**: State that the base of the modern periodic table is atomic number.
- Hint: Summarize the reasoning that led to this conclusion.