How is the modern periodic table of elements primarily arranged?

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

Answer: (A)

Verified step by step guidance

1. Understand that the modern periodic table is organized to reflect the properties of elements in a systematic way.
2. Recall that early versions of the periodic table were arranged by increasing atomic mass, but this caused inconsistencies in element grouping.
3. Recognize that the modern periodic table is arranged by increasing atomic number, which is the number of protons in an atom's nucleus.
4. Know that arranging elements by atomic number ensures that elements with similar chemical properties fall into the same groups or columns.
5. Conclude that the primary arrangement of the modern periodic table is by increasing atomic number, not by atomic mass, discovery order, or alphabetical order.