How is the modern periodic table of elements arranged?

• A. By increasing atomic number
• B. By the order of element discovery
• C. By alphabetical order of element names
• D. By increasing atomic mass

Answer: (A)

Verified step by step guidance

1. Understand that the modern periodic table is organized based on a fundamental property of elements called the atomic number, which is the number of protons in an atom's nucleus.
2. Recall that earlier versions of the periodic table were arranged by increasing atomic mass, but this led to inconsistencies in element properties.
3. Recognize that arranging elements by increasing atomic number resolves these inconsistencies and groups elements with similar chemical properties into columns called groups or families.
4. Note that the periodic law states: The properties of elements are a periodic function of their atomic numbers, meaning elements show repeating patterns of properties when ordered by atomic number.
5. Therefore, the modern periodic table is arranged by increasing atomic number, not by order of discovery, alphabetical order, or atomic mass.