According to modern periodic law, the physical and chemical properties of elements are the periodic functions of their ?

Options

A. Density
B. Atomic Number
C. Mass Number
D. Atomic Mass

Answer

**Step-by-Step Solution:**

1. **Understanding Modern Periodic Law**: The modern periodic law states that the properties of elements are a periodic function of their atomic number. This means that when elements are arranged in order of increasing atomic number, elements with similar properties appear at regular intervals.

2. **Identifying Atomic Number**: The atomic number of an element is defined as the number of protons in the nucleus of an atom. For example, sodium has an atomic number of 11, while lithium has an atomic number of 3.

3. **Grouping of Elements**: Elements that have similar physical and chemical properties tend to be grouped together in the periodic table. For instance, sodium (atomic number 11) and lithium (atomic number 3) are both alkali metals and share similar properties, thus they are placed in the same group.

4. **Conclusion**: Therefore, according to the modern periodic law, the physical and chemical properties of elements are periodic functions of their atomic number.

**Final Answer**: According to modern periodic law, the physical and chemical properties of elements are the periodic functions of their atomic number.

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