How is the periodic table of the elements primarily arranged?

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

Answer: (A)

Verified step by step guidance

1. Understand that the periodic table is a systematic arrangement of elements based on their properties.
2. Recall that early versions of the periodic table were arranged by increasing atomic mass, but this caused inconsistencies in element placement.
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 aligns elements with similar chemical properties into the same groups or columns.
5. Conclude that the primary arrangement of the periodic table is by increasing atomic number, not by alphabetical order, atomic mass, or discovery order.